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PERKINS  LIBRARY 

Duke   University 


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Form  934— 20M— 7-35 


ELEMENTS  fh 

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PHYSIOLOGY. 


IN  TWO  VOLUMES. 


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Elements  of  Phy/wlogy;  A  M 

JO.  FRED.  BLUMENBACH,  m.d. 

PROFESSOR  OF  MEDICINE  IN  ORDINARY  AT  GOc'TTINGEN, 
MEMBER  OF  THE  ROYAL  SOCIETY  OF  SCIENCES  AT 
GOETTINGEN,  AND  OF  SEVERAL  OTHER  SOCIETIES  IN 
DIFFERENT   PARTS   OF   EUROPE. 

Tr -an/lated  from  the  Original  Latin, 

AND 

INTERSPERSED  WITH  OCCASIONAL  NOTES. 
By   CHARLES    CALDWELL. 


TO  WHICH    IS   SUBJOINED,  BY  THE   TRANSLATOR, 

An   APPENDIX, 

EXHIBITING  A  BRIEF  AND  COMPENDIOUS  VIEW 
OF  THE  EXISTING  DISCOVERIES 

Relative  to  the  Subject  of 

ANIMAL    ELECTRICITY 


VOLUME    I. 


PHILADELPHIA, 

PRINTED    BT    THOMAS   I)  OB  SON, 

AT  THE   STONE-HOUSE,  N°4I,  SOUTH   SF.COND-STRt ET. 


M.DCC.XCY. 


& 


T  O 


THE    PROFESSORS 


VARIOUS  BRANCHES  OF  MEDICAL  SCIENCE 
IN  THE  UNIVERSITY  OF  PENNSYLVANIA. 


GENTLEMEN, 

JLiONG  have  you  been  my 
fathers  and  long  my  attentive  pre- 
ceptors',  in  the  interefting  fcience 
of  medicine.  You  juftly  hold  on 
me,  therefore,  a  twofold  claim  for 
the  twofold  duty  of  a  pupil  and  a 
fon.  In  refpeclful  acknowledge- 
ment of  this  undeniable  claim,  I 
now  ftep  forward  and  thus  publicly 
folicit  your  acceptance  of  the  f?f 
fruits  of  that  medical  education, 
which  you  yourfelves  were  pleafed 

to 

275305 


vi.  DEDICATIO  N. 

to  patronize  and  direct  with  fuch 
ability  and  care. 

Avowedly  to  folicit  an  cxtenfion 
of  your  immediate  patronage  and 
protection  to  the  following  tranf- 
lation,  would  be  to  offer  you  an 
indignity  little  lhort  of  aclual  in- 
fult.  Such  a  folicitation  would 
falfely  reprefent  you  as  men  un^ 
willing  to  become  the  fpontaneous 
guardians  and  friends  of  filent, 
un  affirming  truth  and  merit,  but 
{landing  with  open  arms  for  the 
reception  even  of  intrufive  error 
itfelf,  when  ufhered  to  your  notice 
by  a  brazen  front  and  a  blanditious 
tonbue. 

The  original  work  of  Profeffor 
Blumenbach  has  been  already  fane- 

tioned 


DEDICATION.  vii. 

tioned  by  the  applauding  voice  of 
the  learned  and  the  ingenious  in 
aim  oft  every  part  of  the  globe  to 
which  phyfical  fcience  has  hitherto 
found  its  way.  On  the  folitary 
bafis  of  its  own  intrinfic  merit  let 
my  tr (inflation  alfo  Hand ;  or  if, 
indeed,  it  be  deftitute  of  fuch  bafis, 
with  difgracc  let  it  fink  into  that 
fea  of  oblivion  which  fo  juftly 
awaits  its  final  reception. 

From  you,  Gentlemen,  it  is  fe- 
cure  of  at  leaft,  a  patient,  and,  I 
flatter  myfelf,  an  impartial  exami- 
nation. Should  the  execution  of 
the  work  fortunately  meet  with 
your  approbation  and  applaufe, 
you  will  be  its  aufpicious  announ- 
cers to  the  medical  public :  but 
mould  it  appear  to  you  faulty  and 

even 


275305 


viii.  DEDICATION. 

even  wholly  unworthy  of  further 
attention  or  regard,  you  will  not, 
I  am  fure,  lofe  fight  of  that  fa- 
vourite maxim  of  the  humane  and 
generous  bofom,  "  primum  pecca- 
tum  veniandum  e/l" 

Impreffed  with  the  moil  pro- 
found fentiments  of  efteem  and 
gratitude  for  your  favours  of  a 
public  nature,  as  well  as  for  your 
attentive  acls  of  private  friendihip, 
I  have  the  honour  to  be, 

Your  fmcere  Friend, 
And  Pupil, 
Tile  TRANSLATOR, 

PlULArELPHIA,    7 

hebruary  1 1,  179;.  5 


Preface  by  the  Tranjlator. 


Wh  AT  a  fafhionable  letter  of  in- 
troduction is  to  its  bearer,  a  fafhionable  pre- 
face is  to  the  literary  performance  which  it 
openly  announces  to  the  world,  The  former 
procures,  for  the  moil  part,  admiffion,  and, 
at  leaft,  a  dinner  ;  the  latter  moil  commonly 
an  attentive  perufal.  For  their  future  conti- 
nuance, however,  in  favour  and  eileem,  both 
the  vifitant  and  the  volume  muft  depend  on 
fomething  more  fubflantial,  and  of  more  un- 
equivocal utility,  than  either  the  light  eti- 
quette of  a  letter,  or  the  fpecious  propofak 
of  a  recommendatory  preface. 

The 


x  PREFACE. 

The  reader  is  requefted  to  view  the  pre- 
fent  prefatory  add refs  as  a  mere  peace-offering, 
made  by  the  tranflator  to  ancient  and  invete- 
rate cuftom,  and  not  as  afolemn  appeal  to  the 
public  defigned  to  enhance  either  the  merit  of 
the  following  performance,  or  the  uprightnefs 
of  the  motives  which  led  to  its  execution.  For 
with  regard  to  the  merit  of  the  work,  I  flatter 
myfelf  that  no  character  of  literature  and  ta- 
lents will  ever  refign  his  right  of  judging  for 
himfelf ;  and  as  to  the  motives  by  which  I 
was  induced  to  engage  in  its  translation,  they 
are  indeed  at  prefent  nothing  better  than  ab- 
iblute  non-entities,  and  will  in  no  way  elfecl: 
its  utility  to  man. 

The  want  of  a  new  and  complete  fyftem 
of  phyfiology  has  been  long  and  very  fenfi- 
bly  experienced  and  regretted  by  ail  medical 
fludents  on  this  fide  the  Atlantic.  As  to 
myfelf,  I  am  fure  I  was  led  moil  devoutly  to 

regret 


PREFACE.  » 

regret  ftich  a  want,  throughout  every  ftage 
o  f  medical  ftudies.  in  orJe  to  acquire 
a  knowledge  .of  the  improvements  which  had 
lat  taken  pla<  e  in  this  important  branch 
of  phyfical  fcience,  I  was  obliged  to  range 
with  an  infinitude  of  labour  and  attention, 
through  daily  accumulating  volumes,  which 
it  was  fometimes  extremely  difficult  to  pro- 
cure. This  difficulty  was  augmented  even 
to  impoffibility  itfelf  with  thofe  unfor- 
tunately living  out  of  the  fphere  of  public 
libraries, 

The  mutilated  abridgment  of  Haller's 
phyliology,  publifhed  in  the  Fngufh  lan- 
guage, is  (to  ufe  a  common  mode  of  expref- 
iion)  certainly  nothing  more  than  a  bare  apo- 
logy for  a  fyftem.  It  is  imperfect,  erro- 
neous, and,  in  many  places,  to  me  wholly 
Unintelligible.  In  fome  parts,  therefore,  it 
wo  doubt  inculcates  truth,  in  others  implants 

the 


*ii  PREFACE. 

the  feeds  of  error,  and  in  other  places  again 
leaves  the  young  mind  at  liberty  to  indulge 
itfelf  in  all  the  wildnefs  and  revelry  of  con- 
jecture. 

For  thefe  deficiencies  and  faults,  I  am  Hire 
that  at  leafr.  fome  compenfation  is  made,  and 
fome  degree  of  remedy  provided  in  the  fol- 
lowing fheets,  which  I  am  about  to  ufher 
forth  to  the  world.  But  on  this  fu  bjecT  let 
decifion  be  awarded,  and  judgment  pro- 
nounced, by  the  candid  and  intelligent  rea- 
der,  and  not  by 

His  obedient  humble  Servant, 

The  TRANSLATOR. 


CONTENTS, 


VOLUME     r. 


SECTION.  I.     Of  the  living  Human  Bodv  in  general       i 

Sect.  II.     Of  the  Fluids  of  the  Human   Body   in 

general,  and  of  the  Blood  in  particular  -         3 

Sect.  III.  Of  the  Solids  of  the  Human  Body  in 
general,  but  particularly  of  the  Cellular  Mem- 
brane .  .  .  .  .18 

Sect.  IV.  Of  the  Vital  Energies  in  general,  but  par- 
ticularly of  Contractility  .  .  31 

Sect.  V.     Of  Sound  Health,  and  of  the  Nature  of 

Man  ....  39 

Sect.  VI.     Of  the  Motion  of  the  Blood  in  general     48 

Sect.  VII.     Of  the  Arteries  .  .  -54 

Sect.  VIII.     Of  the  Veins  which  carry  Blood.  62 

Sect.  IX.     Of  the  Heart  ...  66 

Sect.  X.     Of    the  Powers  by  which  the    Blood  is 

kept  in  Motion  .  .  .  83 

Sect.  XI.     Of  Refpiration  and  its  Primary  Ufe  97 

Sect. 


xiv  CONTENTS. 

Sect.  XII.     Of  Voice  and  Speech                  .  i  ro 

Sect.  XIII.     Of  Animal  Heat.             .  .           Mq 

Sect.  XIV.     Of  Cutaneous  Perfpiration.  .            126 

Sect.  XV.     Of  the  Senforium  and  Nerves  .           142 

Sect.  XVI.     Of  the  Functions  of  the  Nervous  Syftem 

in  general  .  .  .  .  ^ 

Sect.  XVII.     Of  the  External  Senfes  in  general,  but 

particularly  of  the  Touch  .  .         .  z62 

Sect.  XVIII.     OftheTafte               .              .  166 

£ect.  XIX.     Of  Smelling              .             .  .169 

Sect  XX.     Of  Hearing  ...  173 

Sect.  XXI.     Of  Vifion                .  .             .  .178 

Sect.  XXII.    Of  the  Internal  Senfes  and  other  Facul- 
ties of  the  Mind  .  .195 

Ssct.  XXIII.     Of  thofe  Adions  of  the  Body  which 

are  fubject  to  the  power  of  the  Will  .  201 

S«ct.  XXIV.     Of  Mufcular  Mot'oa.  .  207 

Sect.  XXV.  Of  Sleep.  .  .  22j 


VOLUME 


- 


CONTENTS.  .v. 


VOLUME    IX, 


Sect.  XXVI.     Of  Food,  and  the  Appetite  for  it  i 

Sect.  XXVII.     Of  Maftication  and  Deglutition  8 

Sect.  XXVIII.     Of  Digestion               .               .  16 

Sect.  XXX.  Of  the  Bile               .               .  .28 

Sect.  XXXI.  Of  the  Function  of  the  Spleen         .  45 

Sect.  XXXII.     Of  the  Function  of  the  Omentum  50 

Sect.  XXXIII.  Of  the  Function  of  the  Inteftines  55 
Sect.  XXXIV.     Of  the  Functions  of  the  Abforbent 

Syftem.            .            .            .            „  .65 

Sect.  XXXV.     Of  Sanguification              .              .  78 

Sect.  XXXVI.     Of  Nutrition              .               .  S3 

Sect.  XXXVII.     Of  Secretion                 .               .  9o 

Sect.  XXXVIII.  Of  the  Urine  .  •  10* 
Sect.  XXXIX.     Of  the  Difcrimination  of  the  Sexes 

in  general             .             .              .              .  n0 

Sect.  XL.  Of  the  Genital  Function  of  the  Male  Sex.  1 14 
Sect.  XLI.     Of  the  Genital  Function  of  the  Female 

Sex  in  general  .  .  .  .122 

Sect.  XLII.  Of  Mcnftruation             .  .             141 

Sect.  XLII1.  Of  the  Milk             .             .  .146 

S^ct.  XLIV.  Of  Conception  and  Pregnancy  .         154 

?  Sect. 


xvi  CONTENTS. 

Sect.  XLV.     Of  the  Nifus  Formativus,  or  Formative 

Effort.  .  .  .  .  174 

Sect.  XLVI.     Of  Parturition,  and  its  Confcquences    184 

Sect.  XLVII.      Of  the  Differences    by    which    the 

Human  Subject  is  charaflcrifed  before  and  after 
Birth  .  .  .  .  191 

Sect.  XLVIII.      Of  the    Increafe,    Maturity,     and 

Decline  of  Man  *  .  .  200 


APPENDIX 213 


ELEMENTS. 


ELEMENTS 

OF 

PHTSIOL  0  GT. 

SECTION    I. 

OF  THE  LIVING  HUMAN  BODY  IN  GENERAL. 


I 


§  >• 


N  the  living  human  body,  the  healthy 
fun&ions  of  which  conftitute  the  exclufive  object 
of  the  fcience  of  Phyfiology,  there  occur  three 
things  worthy  of  our  immediate  attention  and 
regard* j  namely, 

The  Solids,  or  parts  containing ; 

*  In  an  ancient  volume  commonly  ranked  among  the  wri- 
tings of  Hippocrates,  Epidemic.  VI.  Sect.  8.  §  19,  we  find  the 
following  remarkable  claufe :  "  Quae  continent  corpora,  aut 
*  intus  continentur,  aut  in  nobis  cum  impetu  moventur 
"  contemplanda  funt."  This  celebrated  claufe  furnifhed 
Abr.  Kaau  Bocrhaave  with  the  firft  hints  and  fuggeftions 
Vol.  I.  A  on 


2  OF  THE  LIVING  HUMAN  BODY. 

The  Fluids,  or  parts  contained  within  the  folids  j 

And  laftly,  the  Vital  Energies,  which  in  the 
confideration  of  the  fe'ence  of  phyfiology,  confti- 
tute  the  moft  interefting  and  important  object  of 
our  regard.  It  is  in  confequence  of  thefe  energies 
that  the  fo'ids  are  rendered  alive  to  the  impulfe  of 
the  fluids,  endued  with  a  power  to  propel  the  fame, 
and  alfo  to  perform  a  variety  cf  other  motions. 
It  mud  however  be  obferved,  that  thefe  energies 
are  not  incommunicably  excluded  even  from  fome 
of  the  fluids  themfelves :  on  the  whole,  they  ap- 
pear to  constitute  the  effence  or  fupreme  charac- 
terise of  an  organifed  body. 

§  2. 
But  although  thefe  three  objecls  have  been  with 
propriety  conlidered  as  diftinct  from  each  other, 
and  may  therefore  be  feparately  enumerated  on 
the  prefent  occafion,  they  are  notwithstanding  in 
the  living  body,  which  is  alone  the  exclufive  fub- 
jecl:  of  phyfiology,  fo  intimately  connected  toge- 
ther, that  it  is  fcarcely  poflible  to  form  even  a 
conception  of  one  without  at  the  fame  time  em- 
bracing the  others. 

on  tht  {abject  of  his  incftimable  work  entitled,  "  Impetum 
"  faciens  dictum  Kippocrati  per  corpus  con&ntiens."   L.  B. 

1745-8. 

The 


OF  THE  FLUIDS,  3 

The  mofl  pure  and  limpid  fluids  of  our  body 
abound  with  animal  earth :  on  the  other  hand, 
though  our  folids  may  appear  to  us  completely 
deftitute  of  liquid  matter,  yet,  befides  the  circum- 
flance  of  their  originating  from  the  fluids  as  their 
matrix  or  primary  fource,  they  contain  in  their 
compofition  an  evident  quantity  of  moifture : 
laftly,  if  we  be  not  deceived,  it  is  certainly  true 
that  there  exifls  fcarcely  a  fibril  in  the  living 
body  which  does  not  poflefs,  in  a  higher  or  lower 
degree,  a  vital  energy  inherent  in  itfelf. 

§3- 

We  now  proceed  to  treat  of  each  of  thofe  three 
obje&s  feparately  and  in  order  :  and  firft  of  the 
fluids  ;  as  conflituting  by  far  the  greatefk^  and 
what  may  be  emphatically  called  the  firji-born 
part  of  our  bodies. 


SECT.    II. 


OF  THE  FLUIDS  OF  THE  HUMAN  BODY  IN  GENERAL, 
AND  OF  THE  BLOOD  IN  PARTICULAR.     , 

§4- 

XA.LL  the  different  fluids  of  our  body, 
may  with  propriety  be  thrown  into  three  leading 
clafles. 

A  2  Thcfe  j 


4  OF  THE  BLOOD. 

Thefe  are,  I.  The  Crude  or  unaflimilifed  fluid, 
confifting  chiefly  of  the  chyle  contained  in  the 
prima?  vise,  and  deftined  for  converfion  into  blood; 
to  which  may  alfo  be  added,  that  fluid  received 
by  abforption  from  the  external  fuperficies  of  the 
body,  and  conveyed  to  the  fame  receptacle  with 
the  former. 

II.  The  blood  itfelf; 

And  Laftly,  the  fecrefed  fluid,  or  that  formed 
from  the  volume  of  blood  by  the  animal  procefs, 
called  fecretion  :  the  fluids  prepared  by  this  pro- 
crfs  are  deftined,  fome  of  them,  to  be  retained  in 
our  body,  to  ferve  further  purpofes  in  the  animal 
economy ;  and  others,  to  be  eliminated  from  our 
f)ftem,  as  wholly  excrementitious. 

§  5- 

Of  the  firfl:  and  third  of  thofe  clafles  we  will 
fpeak  on  a  future  occafion,  when  we  come  to  trtat 
of  chylification,  and  of  fecretion,  together  with  the 
oi!:er  functions  to  which  thofe  fluids  are  rtfpec- 
tively  related.  Let  us  now  proceed  to  the  confe- 
deration of  the  blood,  that  mo  ft  important,  that 
prim?ry,  and  truly  vital  liquid,  which  may  with  the 
great  eft  propriety  be  called,  the  living  fountain 
of  all  the  other  fluids ;  as  being  that  into  which 
the  crude  fluid  is  converted  j  and  from  which  all 

the 


OF  THE  BLOOB.  5 

the  fcrreted  fluids  derive  their  origin  ;  and  which 
(a  few  parts  of  the  body  excepted,  fuch  as  the 
epidermis,  the  tunica  araebnoidea,  the  amnion, 
the  vitreous  fubftance,  or  enamel,  of  the  teeih, 
.&•'.)  fl>ws  uniformly  through  every  even  the 
iTiOff  minute  and  fine  fpun  parts  of  the  inexplicable 
texture  of  our.fyftem. 

§  6. 

The  blood  is  a  liquid  ful  generis,  of  a  well 
known  colour,  more  or  lefs  intenfe  :  it  is  glutin- 
ous and  warm  to  the  touch  :  the  formation  of  this 
liquid  has  hitherto  been  ranked  among  the  arcana 
of  nature,  as  it  has  never  been  fuccefsfully  imi- 
tated by  any  procefs  of  art. 

§7- 

This  vital  liquid  when  recently  drawn  from  a 
living  fubjecl:,  and  received  into  a  veffel,  exhibits 
in  a  very  obvious  manner  the  following  remark- 
able phenomena  : 

In  the  firft  place,  while  it  is  yet  warm,  a  fubtle 
halitus  afcends  from  it,  which  being  colle&ed  in  a 
receiver,  forms  fmail  pellucid  globules,  fimilar  in 
appearance  to  drops  of  dew  ;  it  is  of  an  aqueous 
nature,  refembling  not  a  little  common  fountain 
water,  except  that  it  emits  a  peculiar  nidorous 
fmell,  (ilill  more  confiderable  in  the  blood  of  car- 
A  3  niyorous 


6  OF  THE  BLOOD. 

nivorous  animals)  and  which  may  be  aptly  called 
the  animal  odour  ;  fuch,  for  example,  as  arifcs 
from  frefh  urine,  or  from  the  thoracic  and  abdo- 
minal cavities  of  a  dead  fubject  recently  opened. 
Cf  this  aqueous  liquor  a  confiderable  quantity  re- 
mains in  a  Mate  of  mixture  with  the  other  confli- 
tuent  parts  of  the  blood,  which  (hall  be  hereafter 
mentioned. 

§  8. 

In  the  mean  while,  as  the  blood  contained  in 
the  veflel  fuffers  a  gradual  redu&ion  of  tempera- 
ture, it  begins  to  feparate  into  two  parts.  A 
coa?uhi  n  is  firft  formed,  from  the  fapcrficies  and 
fides  of  which,  there  prefrntly  exfudes  a  liquor 
of  an  intermediate  (hade  between  pale  yellow, 
and  cvanefcent  red,  which  they  call  the  ferum  of 
the  blood  ;  in  proportion  as  this  liquor  accumu- 
lates by  exfudation,  a  correfponding  diminution  is 
obfervable  in  the  volume  of  the  coagulum  itlelf ; 
the  coa  ulum  thus  reduced  in  fize  has  been  dif- 
tinguifhed  by  the  name  of  crajfamentum,  as  alfo 
by  thofe  of  the  liver,  and  placenta  cf  the  blood, 
from  a  refemblance,  in  point  of  colour  and  fran- 
gibility  of  texture,  fuppofed  to  exift  between  it 
and  thefc  two  bo  lies  ;  it  has  been  likewife  called 
the  ijlind,  from  the  circumflance  of  its  being  held 
in  a  natant  or  floating  date  in  the  furrounding 
fen:  m. 

§  9* 


OF  THE  ELOOB.  7 

§  9- 
This  craffamentum  itfelf,  by  a  delicate  treatment, 
fuch  as  gentle  agitation  or  frequent  ablutions  in 
water,  may  be  again  feparated  into  two  constituent 
parts,  viz.  the  cruor,  which  imparts  the  red  co- 
lour to  the  whole  mafs  of  blood,  and  which  by 
ablution  is  carried  off  from  the  lymph,  the  other 
and  more  fubftantial  part,  and  which,  therefore, 
is  called  the  bafis  of  the  craffamentu  n  ;  that  the 
cruor  retains  for  this  bafis  a  much  ftron^er  af- 
finity than  the  ferum  pofTelTes,  is  fufficientiy  ob- 
vious from  this  circurnftance,  that  the  cruor  and 
bafis  cannot  be  difparted  unlefs  by  the  interpo- 
fition  of  a  certain  degree  of  force.  Tlie  lymph 
itfelf  beino:  robbed  of  the  cruor,  becomes  more  and 
more  pale  until  it  finally  affumes  the  appearance  of 
a  white  and  coniiderably  tenaceous  coagulum, 

§  10. 
Such  then  appears  to  be  the  four  principal  con- 
ftituent parts  of  the  blood, — viz.  the  watery 
baUtus ;  the  ferum;  the  cruor,  or  red  globules  j 
and  the  coagulable  lymph;  which  fcveral  parts, 
as  long  as  they  retain  their  native  degree  of  vital 
temperature,  continue  in  a  (late  of  the  moil 
equable  mixture,  conftituting  an  uniform  and 
homogeneous  fluid. 

A  4  It 


8  OF  THE  BLOOD. 

It  will  now  be  proper  to  enter  into  a  more  mi- 
nute confideration  of  thofe  three  portions  of  the 
blood  which  (land  lad  in  the  above  enumeration  : 
As  to  the  aqueous  exhalation  which  we  have  men- 
tioned, it  does,  not  appear  of  fufficient  importance 
to  claim  any  further  attention  ;  indeed  as  it  is  alfo 
difcovered  in  other  parts  of  the  body,  it  cannot 
be  confidered  as  proper  to  the  blood  alone,  any 
more  than  the  air  which  this  vital  fluid  contains, 
and  on  which  we  will  date  a  few  obfervations  in 
a  fubfequent  part  of  this  fe&ion. 

§    «- 

The  ferum  is  a  liquid  of  fuch  a  gelatinous  nature 
as  to  impart  to  the  whole  mafs  of  the  blood  the 
chief  part  of  its  vifcofity  or  gluey  confidence  :  it 
very  much  refembles,  in  all  its  properties,  the  al- 
bumen or  white  of  eggs  ;  when  fubje&ed  to  the 
aftion  of  a  temperature  equal  to  the  150th  degree 
on  the  fcale  of  Fahrenheit's  thermometer,  it  paf- 
fes  into  a  coagulum,  white  and  eafily  broken 
down,  analogous  to  the  white  of  eggs  in  a  boiled 
flate;  it  alfo  differs  a  fimilar  change,  according 
to  the  experiments  of  the  celebrated  Mofcati,  if 
it  be  mixed  with  a  quantity  of  quick  lime,  though 
in  this  cafe  the  coagulation  proceeds  much  raore 
flowly,  and  is  not  completed  till  after  the  twen- 
tieth hour.  But  if  the  fcrum  be  dried  with  a 
gentle  heat,   and  left  wholly  undifturbed,    it  is 

converted 


OF  THE  BLOOD.  '  9 

converted  into  a  firm  pellucid  mafs,  fimilar  in  irs 
external  appearance  to  gum  arabic,  which  in  a 
gradual  manner,  like  the  dried  white  of  eggs, 
cracks  and  forms  over  its  furface  numerous  Juki 
or  fuTures  running  in  a  fomewhat  fpiral  direclrion, 
and  exhibiting  a  very  lingular  appearance. 

§     12. 

Befides  thofe  other  properties   of   the   ferum 
already  mentioned,  there  is  one  highly  worthy 
our  confideration,  to  which  my  attention  was  firft 
called    by    the    experiments    of    the    illuftrious 
Prueilley  *  ;    but   my  belief    of   which  has  fince 
been  fully  confirmed  by  repeated  obfervations  of 
my  own,  viz.  the  facility  with  which  the  air,  fur- 
rounding  a  veflcl  filled  with  blood,  is  able  to  act 
through  the  medium  of  the  ferum  or  the  craifa- 
mentum,  though  deeply  covered  by  the  former,  in 
fuch  a  manner  as  to  produce  a  very  remarkable 
change  in  the  colour  of  the  latter,  whereas,  on 
the  other  hand,  the  fame  a&ion  of  the  air  would 
be  very  much  impeded,  if  not  entirely  prevented, 
if  inflead  of  the  ferum,   the  craflamentum   were 
covered  with  any  foreign  liquid,  fuch  as  water, 
or  oil,  &c.  or  even  with  any  other  fluid  of  the 
human  body  kfelf,  as  the  faliva  or  urine. 

*  Philof.  Tranfatf.  vol.  LXVI.  P.  I.  pag.  244,  feq. 

§  13- 


i*  OF  THE  BLOOD. 

§   *3- 

The  cruor  confcitutcs  another  very  finking  and 
important  part  of  the  blood,  and  is  a  fource  of 
many  Angularities,  whether  we  confider  the 
colour  and  figure  of  its  particles,  or  the  elemen- 
tary parts  into  which  it  is  refolved  when  fubjected 
to  the  acTion  of  an  intenfe  heat.  It  appears  to 
deferve  a  place  among  the  mod  elaborare  juices 
of  the  body,  as  it  feldom  appears  in  the  tender 
fcetus  previoufly  to  the  fourth  week  after  concep- 
tion, nor  in  the  nafcent  young  of  gallinaceous 
fowls  till  the  fortieth  hour  of  incubation.  After 
profufe  hemorrhages  it  like  wife  appears  to  be  re- 
placed by  the  powers  of  the  fyftem,  with  much 
more  difficulty  than  the  other  condiment  portions 
of  the  blood. 

§   14- 

It  confifts  of  globules,  find  obferved  by  Leen- 
wenhbek.  In  blood  recently  drawn  they  are  al- 
ways prefent,  of  a  conftant,  uniform  figure,  and 
of  an  equable  magnitude  ;  which  circumdances, 
added  to  the  further  confideration,  that  in  no 
other  fluid  (milk  alone  excepted,  the  particles  of 
which  are  fo  me  what  analogous),  are  fimilar 
bodies  to  be  met  with,  leave  not  a  fliadow  of 
doubt,  but  that  thofe  globules  form  a  part  very 
obvioufly  and  eilentially  different  from  the  other 
condiment  portions  cf  the  blood,  though  at  the 

fame 


OF  THE  BLOOD.  1 1 

fame  time  the  formation  of  thofe  globular  bodies 
thenfelves  appears  in  reality  to  be  much  more 
fimple  than  iome  celebrated  characters  would  in- 
duce us  to  believe.  For  to  pafs  over  in  filence 
the  complexity  of  the  fixfold  form  iiclitiouflv  be- 
llowed on  them  by  Leeuwenhoek,  neither  the  an- 
nular figure  attributed  to  them  by  the  illuftrious 
de  la  Torre,  nor  the  form  of  veficles  enclofing  an 
opaque  nucleous,  fuch  as  Hewfon  apprehended  he 
difcovered  in  them,  have  appeared  to  me  to  be 
well  founded*.  In  my  obfervations,  indeed,  I 
have  been  able  to  detedl:  nothing  more  than  bodies 
of  a  fimple  fpherical  appearance,  and,  if  I  am  not 
deceived,  of  a  folid  gelatinous  confidence.  I  have 
not,  indeed,  abfolutely  denied  the  lenticular  figure 
bellowed  on  them  by  fome  observers :  I  dare  not, 
however,  venture  to  affert,  that  I  have  been  fo 
fortunate  as  to  obferve  it. 

It  has  been  a  fubjeft  of  controverfy  whether  or 
not  they  can  alter  their  figure  when  it  becomes 
neceifary  for  them  to  pafs  through  a  veflel  of  a 
very  narrow  diameter.  I  am  inclined  to  believe, 
in  conformity  to  the  opinion  of  that  accurate 
obferver  Reichel  that  under  the  above  circum- 
flances,  they  do  actually  change  their  fpherical 
for  an  oval  figure,  and  again  refume  their  former 

»  Philof.  Tranf.  Vol.  LXIII.  P.  II.  p.  303.  faj.  tab.  XII. 

globular 


iz  OF  THE  BLOOD. 

globular  fhape,  when  they  advance  into  vcfTels 
fufficien  ly  capaciou-s ;  though  I  mud  confvfs,  I 
never  had  the  happinfs  to  be  a  fpc&ator  of  this 
interefting  phenomenon. 

This  fpherical  figure  of  the  globulus  is  never 
perceived  unlefs  in  the  blood  circulating  in  the 
veffels  of  a  living  animal,  or  in  that  -which  is  re- 
cently drawn  ;  they  lofe  all  regularity  of  form  in 
procefs  of  time,  and  appear  to  dhTolve,  as  it  were, 
and  again  unite  with  each  other  into  one  uniform 
ihapelefs  mafs. 

§  '5- 

Phyfiologifts  differ  in  determining  the  fize  of 
the  globules  of  the  blood.  Hales  reckons  them 
equal  in  diameter  to  the  -r*Wh  part  of  an  inch. 
Senac  eftimates  their  diameter  at  about  the  TT««th 
part  of  the  f  ime  meafure,  while  others  again  en- 
tertain different  opinions. 

§  .6. 

Their  colour  is  red,  and  therefore  the  beautiful 
cri.Vifon  caffc  of  the  whole  mafs  of  blood  appears 
to  be  evidently  derived  from  them.  The  intenilty 
of  this  colour  changes  with  a  multiplicity  of  vary- 
ing circumftances  ;  it  is  more  pale  in  animals  which 
ate  too  fparingly  nourilhed,  or  in  fuch  as  have 
fullered  profufe  hemorrhages.  The  blood  con- 
contained 


OF  THE  BLOOD.  13 

tained  in  the  arteries  is  imre  florid,  together  with 
that  which  has  been  Subjected  to  the  action  of 
atmofpheric,  but  more  efpecially,  that  which  has 
been  expofed  to  dephhgifticated  air  ;  while  venous 
blood  is  more  obflure,  as  well  as  that  which  has 
been  acted  on  by  fixed  or  inflammable  air. 

§   l7- 
Upon  the  whole,  the  caufes,  which  augment 

the  quantity  of  the  red  globules  in  general,  and 
alfo  heighten  the  intenfny  of  their  colour,  are 
fufficiently  evident  :  but  to  difcover  from  what 
fecret  fmrce  their  difpofition  to  this  crimfon  dye 
is  originally  derived,  is  a  matter  of  Herculean 
difficulty  indeed.  Haller  afcribed  it  to  the  pre- 
fence  of  crocus  martis,  becaufe  the  blood  abounds 
more  with  iron  than  the  bones,  or  other  parts  of 
the  body,  although  the  quantity  contained,  even 
in  the  blood  itfelf,  is  very  fmall ;  and  although 
authors  differ  aftonifhingly  in  their  attempts  to 
afcertain  it.  Thus,  for  inilance,  Menghinus  efti- 
inated  its  relative  proportion  to  the  whole  mafs  of 
the  blood,  to  be  as  1  to  110;  whereas,  the  illus- 
trious Rhades  calculated  it  to  be  only  as  1  to  427  ; 
and  again,  in  fome  future  experiments,  to  be  no 
more  than  as  1  to  503,  &c. 

On  the  prefent  Subject  it  feems  proper  to  make 
the  following  obfervation  ;  viz.  that  no  iron  can 

be 


1 4  OF  THE  BLOOD. 

be  difcovered  in  the  cruor  of  the  blood  unlefs  it 
be  previoufly  calcined ;  whereas,  on  the  other 
hand,  when  it  was  dried  with  a  gentle  heat,  and 
reduced  to  the  mod  impalpable  powder,  I  could 
not  obferve  a  tingle  particle  of  it  attracted  by  the 
magnet,  whether  the  experiment  was  made  in 
water,  or  in  that  mod  fluid  of  all  vehicles,  quick- 
filver. 

§  18. 

We  now  come  to  the  consideration  of  that  con- 
diment part  of  the  mafs  of  blood,  which  dands 
lad;  in  our  order  of  enumeration,  viz.  the  Lymph; 
which  is  by  fome  called  the  bafis  of  the  craflamen- 
tum,  by  others,  the  mucous  or  glutinous  part, 
and  by  others,  the  fibrous  portion  of  the  blood. 

This,  in  former  times,  was  very  erroneoufly 
confounded  with  the  ferum,  from  which  it  is  not- 
withftanding  very  widely  different,  in  all  its  effen- 
tial  properties.  When  the  lymph  is  expofed  to  the 
action  of  air,  efpecially  of  fuch  as  is  of  a  low  tem- 
perature, it  is  immediately  coagulated  ;  but  by  the 
admixture  of  quicklime,  (which  has  been  already 
faid  (§  11.)  to  have  the  power  of  coagulating 
ferum),  it  is  preferved  in  a  fluid  date  ;  or,  even 
though  it  be  already  coagulated,  yet,  by  the 
addition  of  this  fubdance,  it  is  again  immediately 
refolved. 

§    19- 


OF  THE  BLOOD.  15 

We  have  already  touched  on  the  methods,  by 
which  this  part  of  the  blood  may  be  feparated 
from  the  cruor  (§  9.).  It  »»  alfo  by  otncr  artifi- 
cial  methods,  fuch  as  whipping  or  agitating  the 
blood  with  fmall  twigs,  induced  to  aflame  the 
appearance  of  a  membrane,  which  has  been  named 
after  Ruyfch  its  celebrated  difcoverer. 

The  fimilitude  which  prevails  between  the  mem- 
brane thus  formed  by  art,  and  certain  remarkable 
phenomena  in  difeafes,  efpecially  in  thofe  of  an 
inflammatory  nature,  reduces  it  to  a  certainty, 
that  fuch  phenomena  are  to  be  entirely  referred 
to  the  coagulation  of  the  lymph,  of  which  we  arc 
now  treating. 

It  may  be  proper  on  the  prefent  occalion  to 
mention  a  few  of  thofe  numerous  phenomena  al- 
luded to,  which  evidently  derive  their  origin  from 
this  property  of  the  lymph  ;  thus  we  may  inftance 
in  particular,  the  pleuritic  cruji,  which  is  formed 
on  the  furface  of  the  craffamentum  of  blood  re- 
ceived into  a  veflel  and  fuffered  to  remain  fomc- 
time  at  reft  ;  the  membrane-like  appearances  which 
ufually  tranfude  from,  and  completely  invert  the 
furfaces  of  the  feveral  vifcera  when  in  a  flate 
of  inflammation  j  and  alfo  the  membrana  caduca 

of 


16  OF  THE  BLOOD. 

of  Hunter,  which  exfudes  from  the  cavity  of  the 
uterus,  when  impregnated,  and  ftill  under  the 
gentle  alow  of  the  venereal  orgafm.  From  the 
fame  fource  originates  likewife,  that  production  of 
cellular  m.mbrane  by  which  we  fee  frequently  the 
lungs  connected  to  the  pleura  in  cafes  of  peripneu- 
mony ;  as  alfo  the  preternatural  portions  of  the  fame 
fubftancc  often  found  in  the  cavity  of  the  abdomen 
after  profufe  hemorrhages  ;  and  finally,  to  no  other 
fource  can  we  rationally  refer  thofe  membrane- 
like productions,  which,  in  that  lingular  fpecies 
of  difeafe,  vulgarly  denominated  Lithopcedion, 
firmly  attach  to  the  contiguous  vifcera  fuch  parts 
as  are  irritated  to  inflamation  by  the  too  long  re- 
tention of  the  calculus  or  (tone  in  the  abdominal 
Cavity.  It  feems  to  be  alfo  an  opinion  founded  at 
lead  on  probability,  that  polypi,  and  fuch  like 
preternatural  coagulated  excrefcences,  owe  their 
exiftence  to  the  fame  caufe. 

§  20. 
Thofe  phenomena  juft  enumerated,  together 
with  a  variety  of  others  which  every  where  occur, 
demonfhate,  in  a  moil  ftriking  manner,  the  fuperior 
importance  of  this  lymphatic  portion,  in  which 
the  viral  principle  of  the  blood  appears  immedi- 
ately to  refide,  if  indeed  the  blood  poflefs  any  fuch 
principle,  an  opinion  which  I  think  both  ingeni- 
ous and  highly  probable. 

2  Befides 


OF  THE  BLOOD.  17 

§    21. 
Befides  thofe  general  portions  of  the  blood  al- 
ready enumerated,  we  have  on  a  former  occafion 
obferved  that  this  fluid  contains  alfo,  in  a  fhue  of 
mixture,  other  elementary  principles.   (§  10.) 

What  I  principally  advert  to  at  prefent  is  air, 
which  is  commonly  believed  to  conflitute  tt  part 
of  the  whole  mafs  of  blood,  but  which  in  the 
blood  of  a  living  and  healthy  fubject  does  not 
exifl  in  a  free  and  perfectly  elaftic  (late,  but  is  fo 
intimately  united  and  involved,  and  fo  permanent- 
ly fixed,  as  to  be  with  difficulty  extricated  and 
reflored  to  its  native  triform  ftate.  Indeed  I 
have  learned  from  actual  experiments,  that  even  a 
very  fmall  quantity  of  the  moil  pure  air  injected 
through  an  artificial  opening  into  thejugular  vein 
of  a  dog,  has  excited  fymptoms  of  a  very  formida- 
ble nature,  fuch  as  palpitations  of  the  heart,  drowfi- 
nefs,  convulfions,  and,  when  the  quantity  was  flight- 
ly  increafed,  even  death  itfelf  quickly  fucceeded. 

§  22. 
The  elementary  parts  of  the  blood  thus  concife- 
ly  treated  of,  differ  very  widely  in  the  proportion 
they  bear  to  each  other  in  different  fubjects,  ac- 
cording to  the  complex  ratio  of  age,  nourifhment, 
and  other  circumflances  of  importance,  which  re- 
gard the  foiled  health  of  each  individual. 
vol.  1.   „  B  §   23. 


fS  OF  THE  SOLIDS. 

§  23. 
Neither  has  any  thing  more  certain  or  decifive 
been  advanced  with  refpecl  to  the  proportion  which 
the  whole  volume  of  blood  bears  to  the  entire 
bulk  of  the  body.  Haller  was  of  opinion,  that  in 
an  adult  it  amounts  to  30  or  36  pounds  by 
weight  y  while  the  calculations  of  others  have  been 
widely  different. 


SECT.     IIL 


OF  THE  SOLIDS  OF  THE  HUMAN  BODY  IN  GENERAL, 
BUT  PARTICULARLY  OF  THE  CELLULAR  MEM- 
BRANE. 


§    24. 


X  HE  folids  of  the  body  are  originally 
derived  from  the  fluids  themfelves ;  thus  in  the 
firfl  rudiments  of  the  embryo,  while  yet  in  a  gela- 
tinous ftate,  the  folids,  each  in  its  own  appropriate 
fituation,  begin  in  a  very  gradual  manner  to  af- 
fume  their  proper  form  and  texture,  infinitely  dif- 
ferent from  each  other  in  point  of  cohefion,  from 
the  molt  tender  and  almoft  pultaceous  confidence, 
fuch  as  the  medullary  fubftance  of  the  brain,  to 
the  moft  firm  and  durable,  as  the  vitreous  cortex, 
or  enamel  of  the  teeth. 


OF  THE  SOLIDS.  19 

§  25. 
In  all  the  folids  of  the  body  an  earthy  bafis  of 
a  calcareous  nature  abounds  more  or  lefs,  not  in- 
deed in  a  fimple  (late,  but  united  to  the  phof- 
phoric  and  faccharine  acids,  the  former  of  which 
exifts  in  by  far  the  largeft:  proportion.  Their  co- 
hefion  depends  not  only  on  the  peculiarity  of  their 
texture,  but  is  alfo  much  promoted,  as  well  by 
the  quantity  of  air  contained  in  them  in  a  fixed 
date  '*,  (which  is  afcertained  by  the  experiments 
of  the  illuftrious  Hales  to  be  more  abundant  as  the 
parts  are  more  folid)  ;  as  alfo  by  the  fubftance 
called  animal  glue,  which  is  procured  in  large 
quantities  from  the  folid  parts  of  animal  bodies, 
and  is  in  general  ufe  in  fome  of  the  mechanical  arts. 
The  origin  of  this  tenacious  fubftance  may  be 
very  eafily  explained  and  comprehended  from 
what  has  been  already  faid  refpecYing  the  vifcofity 
or  gluey  nature  of  the  blood. 

*  "  The  properties  and  powers  of  air  have  not  yet  been 
ultimately  developed.  It  is,  however,  in  the  mean  time 
certain,  that  this  fubftance  conftitutes,  at  leaft,  a  part  of  the 
gluten  or  cement  by  which  all  the  more  compact  bodies 
in  nature  are  confolidated  and  bound  together.  Thus  the 
diflblution  of  metals,  bones,  ftones,  fhells,  and  falts,  is  uni- 
formly attended  with  an  extrication  of  air."  See  Haller  de 
corp.  hum.  funclionib.     Vol.  III.  pag.  271. 

B  2  The 


to  OF  THE  SOLIDS. 

The  elementary  fubftance  of  iron,  to  which  has 
been  attributed  the  import  ant  office  of  increafmg 
the  powers  of  ohefion  in  the  diiFerent  parts  of 
the  human  body,  fcarrely  deferves  to  be  taken 
into  confiderat'.on  at  aU.  as  I  have  found  its  quan- 
tity to  be  fo  very  minute  as  uot  to  exiil  in  a 
greater  proportion  than  one  fifth  part  of  a  grain 
to  two  rounds  even  of  the  bones,  the  hardeft  and 
mux   coherent  parts  of  the  auimal  fyftem. 

§  26. 
A  great  portion  of  the  folids  of  our  body  very 
evidently  exhibits  a  fibrous  texture,  compofed  of 
fmall  filaments  running  more  or  lefs  parallel  to 
each  other.  Thefe  filaments  or  fibres  may  be 
evidently  enough  perceived  in  the  bones,  efpe- 
cially  the  bones  of  a  foetus,  in  the  mufcular  flefli, 
in  tendons,  ligaments,  aponeurofes,  and  fome  mem- 
branes, as  the  dura  mater,  &c. 

§  27- 
In  various  other  parts  of  the  animal  body,  the 
texture  is  fo  widely  different  from  that  of  which 
we  have  juft  fpoken,  that  in  them  it  is  fcarcely 
poffible  to  trace  the  appearance  of  a  fingle  fibre ; 
their  ftrudlure  is  indeed  ora  very  lingular  and  fpe- 
cific  nature,  diftinguiflied  in  Greek  by  the  name 
parenchyma.  This  parenchymatous  fubftance  is 
almoft  exclufively  confined  to  fome  of  the  fecreting 

vifcera 


OF  THE  SOLIDS.  <u 

rifcera  of  the  fyftem  ;  thus  it  exifts  in  the  kidncs, 
in  the  liver,  Szc.  though  afTuming  a  fomewhai  .li- 
ferent and  peculiar  appearance  in  each. 

§  28. 

Through  all  thofe  varieties  of  compofkion  and 
texture,  whether  of  a  fibrous  or  parenchymatous 
appearance,  there  is  interwoven,  in  common,  more 
or  lefs  of  a  certain  web-like  fubfiance,  which  is 
called  cellular  membrane,  and  which  defcrves  a 
place  among  the  primary,  the  molt  important  and 
elTential,  conftituent  parts  of  our  fyftem. 

§  29. 
For,  in  the  firfl:  place,  there  are  feveral  of  the 
-folid  parts  of  the  human  body,  which  appear  to 
confift  of  little  elfc  than  cellular  membrane,  in  a 
conllipated  or  compared  (late  ;  of  this  defcription 
are  moil  of  the  membranes  and  cartilages  ;  which, 
by  long  maceration,  may  be  again  refolved  into  a 
cellular  web,  of  more  or  lefs  laxity.  It  is,  again, 
fo  intimately  and  minutely  interwoven  in  the  com- 
pcfition  of  other  parts,  as  to  ferve  the  important 
purpofes  of  a  receptacle  and  bafis  to  the  other 
portions  of  fubftance  which  aflift  in  their  formation. 
Thus,  for  inftance,  the  hardeft  bones  made  their 
firfl  appearance  in  the  tenderer  ftate  of  cartilage, 
which,  as  already  obferved,  is  nothing  more  than 
condenfed  cellular  membrane:  this  cellular  mem- 
brane,  yet  Id  a  lax  condition,  became  afterwards 

B  3  diftended^ 


*2  OF  THE  SOLIDS. 

diftended,  and  at  length  completely  faturated,  as 
it  were,  by  the  conftant  acceilion  of  offeous  matter, 
till  it  finally  aflumed  the  nature  and  appearance  of 
perfect  bone.  Indeed  it  would  appear,  that  none 
of  the  folids  of  our  body  exift,  without  containing 
more  or  lefs  of  this  web-like  fubffance  in  their 
compofnion,  if  we  except  the  enamel  of  the  teeth, 
in  which  I  was  not  able  to  difcover  the  fmallefl  por- 
tion of  cellular  fubltance,  even  when  the  enamel 
was  fubje&ed  to  the  action  of  one  of  the  flronger 
acids. 

§   3°- 
This  cellular  Jubilance,  which  ferves  the  great 

purpofe  of  a  boundary,  or  partition-wall,  to  adja- 
cent parts,  is  efpecially  interwoven  in,  as  well  as 
fpread  between,  mufcles  and  membranes.  To  other 
parts,  again,    particularly  to  veffels  and  nerves, 

it  anfwers  as  a  bed  or  bafis  of  fupport.  Finally, 
it  conftiiutes  one  common  and  general  bond  of 
union,  which  connects  the  neighbouring  individual 
parts  to  each  other,  and  eftablifhes  between  the 
whole  an  extenfive  medium  of  communication, 

§  31- 
From  what  has  been  already  faid,  two  conclu- 
sions naturally  prefent  themfelves, 

Firft,  in  as  much  as  it  appears,  that  the  cel- 
lular membrane  certainly  conflitutes  the  ground- 
work 


OF  THE  SOLIDS.  23 

work  of  the  ftru&ure  of  the  whole  body,  if  we 
figure  to  ourfelves  the  entire  removal  of  every 
other  fubftance  which  enters  into,  and  affifts  in 
completing,  ihe  compofition  of  the  fyftem,  the 
cellular  membrane,  (till  remaining  in  its  proper 
fituation,  unmolefled  and  alone,  will  neverthelefs 
preferve  and  exhibit  the  complete  figure  of  the 
whole  and  every  part  of  the  body. 

Secondly,  as  by  means  of  this  cellular  founda- 
tion, a  certain  connection  and  medium  of  commu- 
nication are  formed,  between  all  the  parts  of  the 
body,  however  widely  different  from  each  other 
they  may  be,  in  nature,  or  remote,  in  fituation  ; 
the  knowledge  of  this  fail:  ferves  an  important  end, 
not  only  in  deciding  controverfies  which  refpedt. 
the  continuation  of  membranes,  but  alfo  in  explain- 
ing many  phenomena  of  difeafes  which  daily  pre- 
fent  themfelves. 

§  32- 
As  the  cellular  membrane  appears  thus  to  afford 
origin  and  foundation  to  moft  of  the  folid  parts  of 
the  body,  fo  it  appears  itfelf  to  owe  its  own  exif- 
tence  to  the  lymphatic  part  of  the  blood,  of  which 
we  have  already  fpoken.  I  am  induced  to  enter- 
tain this  opinion  from  having  feen  the  lymph,  after 
tranfuding  from  the  lungs  of  pleuritic  patients, 
converted  by  the  powers  of  the  animal  economy 
B  4  into 


^4C  OF  THE  SOLIDS. 

into  real  cellular  fubftance,  which  afterwards 
affirming  the  appearance  of  more  compacted  mem- 
branes, oftentimes  attaches  thofe  vifcera  to  the 
furrounding  pleura, 

§  33- 
What  has  been  already  advanced  on  the  fubject, 
may  be  fufficient  to  ihow  the  general  nature,  and 
eflablifh  the  importance,  of  the  cellular  membrane. 
We  will  now  proceed  to  coniider  fome  of  its 
varieties. 

And,  in  the  firft  place,  its  firmnefs  is  not  always 
uniform. 

For,  in  general,  other  circumftances  being  alike, 
the  cellular  membrane  of  the  human  body  is  very 
tender  indeed,  when  compared  with  that  of  other 
animals.  If  I  am  not  deceived,  this  very  foftnefs 
and  pliancy  of  the  cellular  fubftance  in  the  human 
fyftem,  deferves  to  be  ranked  among  the  leading 
prerogatives  of  man  ;  becaufe,  in  confequence  of 
it,  his  fufceptibility  of  impreffions  from  the  more 
refined  and  fubtle  ftimuli  is  greatly  increafed,  as 
well  as,  his  capacity  to  perform  motions  and  vari- 
ous functions,  with  facility  and  perfection. 

But  with  regard  to  the  more  lax  or  firm  texture 
gf  the  cellular  membrane.,  even  among  mankind 

themfelves, 


OF  THE  SOLIDS.  iS 

themfelves,  a  very  great  variety  occurs,  depend- 
ing on  age,  fex,  mode  of  life,  climate,  &c. 

Finally,  the  condition  of  this  membrane  as  to 
denfity  and  flrmnefs,  is  various,  as  it  is  found 
exifting  in  different  parts  of  the  fame  body  :  thus, 
it  is  more  lax  on  the  eye-lids  and  prepuce,  more 
compa£l  and  firm  about  the  ears,  &c. 

§  34- 
We  now  proceed  to  confider  another  ufe  or 
office  of  the  cellular  membrane,  befides  that 
which  we  have  already  faid  it  performs  to  the 
body  in  general,  (§  29,  30)  ;  namely,  that  by 
means  of  its  numerous  fmall  cells,  it  affords  con- 
venient temporary  receptacles  for  fluids  of  different 
kinds. 

That  fluid,  which  thofe  minute  cells  are  more 
particularly  deftined  to  receive,  is  a  fine  halitus  of 
a  ferous  nature,  or  a  very  fubtle  Water,  by  which 
almofl  all  parts  of  the  body  are  moiffened,  and 
lubricated,  and  which  this  cellular  web  appears  to 
abforb,  after  the  manner  of  a  fponge  *. 

If  it  be  admifTible  to  defignate  by  the  name  of  vefels, 
thofe  minute  interj}iccs  of  the  cellular  membrane,  by  which 
it  abforbs  fluids  after  the  manner  of  a  fponge,  I  readily 
acquiefce  in  the  opinion  of  William  Hunter,   (fee  Medic. 

Obf. 


26  OF  THE  SOLIDS. 

§  35- 
But,  befides  this,  the  cellular  membrane,  ia 
certain  parts  of  the  body,  ferves  as  a  refervoir  to 
humours  of  a  different  and  fomewhat  fpecific  na- 
ture. Thus,  that  portion  of  it  which  conftitutes 
the  vitreous  fubftance  of  the  eye,  is  charged  with 
a  fluid  of  the  fame  name  : 

That  which  forms  the  meddullary  membrane 
of  the  bones  (commonly,  though  improperly,  cal- 
led the  internal  periofleum)  contains  the  medulla  : 

and, 

Finally,  A  large  portion  interwoven  through 
the  foft  pans  of  the  body,  furnHhes  a  convenient 
receptacle  for  the  other  portions  of  oily  fubftance. 

Obf.  and  Inquiries,  vol.  ii.  p.  27.  feq.)  that  this  web-like 
expansion,  now  under  immediate  coniideration,  is  compofed 
of  a  congeries  of  veffels,  in  like  manner  with  the  other  parts 
of  the  body.  But  if  he  entertained  a  belief,  that  this  mem- 
brane confifts  of  fmall  cylindrical  veins,  which  anatomills 
commonly  mean  to  reprefent  by  the  term  veffe/s,  I  muft 
acknowledge,  that  microfcopical  obfervations,  conducted 
with  the  utmofl  degree  of  minutenefs,  and  the  mofl  cautious 
circumfpecuon,  have  not  been  fufficient  to  furnifh  me  with 
any  unequivocal  teitimony  that  fuch  veflels  actually  exift, 
but  have  rather  induced  me  to  embrace  a  contrary  opinion. 

S  36, 


OF  THE  SOLIDS.  27 

§  36. 
And  here  indeed  a  threefold  variety  prefents 

itfelf  to  our  confideration  : 

There  are,  in  the  firft  place,  certain  parts  of 
the  body,  the  cellular  fubftance  of  which,  though 
of  a  very  foft  and  extremely  flaccid  nature,  is 
notwithstanding,  never  filled  with  fat  in  a  healthy 
fubje-ft. ;  fuch,  for  inftance  is  that  which  lines  the 
eyelids,  and  that  fpread  on  the  genital  organs  of 
the  male,  Sec.  But  further,  in  numerous  parts 
throughout  the  body,  there  are  not  unfrequently 
found  irregular  and  tranfient  collections  of  fat, 
which  appear  to  refide  in  the  fame  kind  of  cells, 
which  at  other  times  aft  as  refervoirs  to  the  atte- 
nuated ferous  fluid  already  mentioned. 

But  finally,  in  certain  parts  of  the  body,  and, 
unlefs  I  am  deceived,  in  cells  of  a  peculiar  nature, 
and  given  defcription,  fat  is  found  conftantly  en- 
clofed,  defigned  to  fubferve  dated,  uniform,  and 
fpecific  ufes  in  the  animal  economy,  fuch,  for  ex- 
ample, is  that  which,  in  the  female  fyftem,  forms 
the  mom  veneris,  which  appears  to  me  to  confti- 
tute  a  very  peculiar  and  completely  circumfcribed 
protuberance  *. 

*  This  circumftance  I  had  an  opportunity  of  afcertaining 
in  a  much  more  fatisfaclory  manner  in  the  dead  body  of  a 
female  ape.  After  having  for  fome  time  fubjecled  the  corpfe 
%o  the  action  of  cold,  I  was  able,  by  removing  the  fkin,  to 

expofp 


28  OE  THE  SOLIDS. 

§  37- 
On  the  fubjeft  of  the  fit  itfelf  we  will  now  pro- 
ceed to  make  a  few  observations,  this  being  fo 
very  proper  a  place  for  entering  on  the  confidera- 
tion  of  it. 

It  is  an  oil,  not  unlike  the  un&uous  oils  of  ve- 
getables ;  bland,  inodorous,  and  lighter  than 
water,  confiding  of  phlogifton,  united  to  phlegm 
by  means  of  an  acid  of  a  peculiar  nature. 

§  $8. 

It  is  formed  at  fo  late  a  period  in  the  foetus, 
that  fcarcely  an  indubitable  veftage  of  it  can  be 
difcovered  earlier  than  the  fifth  month  after  con- 
ception. 

Its  confidence  is  various  in  different  parts  of 
the  body.  That  for  inftance  which  lines  the  in- 
fide  of  the  orbit  of  the  eye,  is  more  fluid,  whilft 
that  on  the  contrary  which  furrounds  the  kidneys 
approaches  to  the  firmnefs  and  appearance  of  faet. 

§  39- 
A  controverfy  has  cxifted  with  refpeel  to  the 
fecretion  of  this  fubflance,  namely,  whether  it  is 
performed  by  a  peculiar  fet  of  glandular  bodies, 

expofe  entire  the  circumfcribcd  globe  of  fat  fituated  beneath 
the  pubes. 

agreeably 


OF  THE  SOLIDS.  29 

agreeably  to  the  opinion  of  William  Hunter,  or 
whether  it  merely  tranfudes,  by  fimple  diapedefis, 
through  the  patulous  mouths  of  arteries  ?  The 
latter  of  thefe  opinions,  befides  other  arguments 
which  might  be  advanced  in  its  favour,  appears 
the  mod  probable  from  hence,  that  not  unfre- 
quently  preternatural  collections  of  fat  have  been 
difcovered  in  other  parrs  than  thofe  commonly  oc- 
cupied by  this  fubftance  :  this  circumftance  can  be 
much  more  aptly  and  rationally  explained  by  at- 
tributing fuch  unufual  collections  of  fat  to  an  error- 
loci,  arifing  from  a  morbid  flate  or  difpofition  of 
the  veiTels,  than  by  referring  it  to  an  unnatural 
and  recently  formed  fyftem  of  glands :  thus  for 
example,  in  the  very  ball  of  the  eye  itfelf,  fat  has 
been  fometimes  found  ;  and  a  fubftance  of  a  na- 
ture like  fuet,  ufua'ly  fills  up  the  cavity  from 
which  a  teflicle  has  been  extra&ed  ;  indeed  there 
fcarcely  exifts  a  cavity  in  the  body  in  which  ftea- 
tomatous  collections  have  not  made  their  appear- 
ance. 

But  to  conclude ;  thofe  fmall  glands  to  which 
certain  celebrated  characters  have  been  folicitous 
to  attribute  the  fecretion  of  fat,  appear  as  yet  to 
be  in  reality  nothing  more  than  mere  creatures  of 
analogy. 


But 


3o  OF  THE  SOLIDS. 

But  however  this  may  be  determined,  it  is  in 
the  mean  time  very  certain,  that  both  the  fecre- 
tion  and  abforption  of  this  fubftance  can  be  per- 
formed with  the  utmoft  difpatch. 

§  4o. 
The  ufes  of  the  fat  are  numerous.  It  lubri- 
cates the  folids,  and  thus  facilitates  motion.  It 
obviates  and  prevents  a  morbid  excefs  of  fenfibi- 
lity.  It  a&s  as  a  defence  againft  cold :  and, 
finally,  by  its  uniform  diftention  of  the  ikin,  con- 
tributes to  comelinefs  and  beauty.  Not  to  men- 
tion the  peculiar  ufes  of  the  fatty  matter  con- 
ftantly  bellowed  on  certain  parts  of  the  body,  as 
the  medulla  of  the  bones,  &c. 

This  fubftance  appears,  however,  to  contribute 
fcarcely  any  thing  to  the  nourifhment  of  the  hu- 
man fpecies  *,  when  in  the  enjoyment  of  entire 
health. 


*  That  bloodlefs  infecfts,  however,  derive  a  principal  part 
of  their  nourifhment  from  the  fatty  fubftance  with  which 
their  bodies  are  plentifully  fupplied,  is  a  conjecture  of  natu- 
ralifts  founded  at  lead  on  probability. 


SECT. 


OF  THE  VITAL  ENERGIES.  31 

SECT.    IV. 

OF  THE  VITAL  ENERGIES  IN  GENERAL,  BUT 
PARTICULARLY  OF  CONTRACTILITY. 

§   41- 

VVE  enter  now  on  the  confideration  of 
a  difficult  fubjeft,  namely,  the  living  folid,  and 
fhall  attempt  a  full  account  of  the  vital  energies, 
by  which  the  different  parts  of  our  body  appear 
to  be  animated  and  fitted,  as  well  to  receive  the 
impulfe  of  ftimuli,  as  to  perform  the  various  mo- 
tions which  are  neceffary  in  the  economy  of  the 
living  fyftem. 

§  42. 
But  with  refpeft  to  the  living  folid,  it  will  firfl: 
be  neceiTary  to  afcertain  its  exaft  limits,  and  to 
define  it  with  precifion  and  accuracy ;  whence  it 
will  evidently  appear,  that  it  is  not  our  intention, 
on  the  prefent  occafion,  to  treat  either  of  thofe 
properties,  which  the  human  body  pofTeffes  in 
common  with  numerous  other  bodies  in  nature, 
fuch  as  elaflicity  (the  powers  of  which,  however, 
are  notwithftanding  exhibited  in  various  motions 
and  functions  of  the  animal  economy),  nor  yet  of 
thofe  which  refide  exclufively  in  the  mind ;  tho* 
we  flatter  ourfelves  no  one  will  deny  the  powerful 
influence  of  thefc  latter  over  the  energies  pofTefT- 

ed 


32  OF  THE  VITAL  ENERGIES. 

ed  by  the  living  folid  itfelf,  confidercd  us  a  mate- 
rial body.  We  will  confine  ourfelves  folely  to 
the  confideration  of  thofe  energies  which  refide  in 
our  body  as  a  fyftem  of  organifed  matter,  and 
which  appear  to  be  related  to  each  other  in  the 
following  order. 

§  43- 

The  firfl:  and  moil  univerfal  fpecies  of  thofe  vi- 
tal energies,  and  which  may  indeed  be  regarded  as 
an  inferior  degree  of  the  others,  or  rather  as  the 
threfliold  leading  to  them,  is  fimple  contraflility, 
i.  e.  a  propenfity  in  a  part  to  contract  itfelf.  As  this 
property  appears  in  reality  to  refide  in  every  part  of 
the  cellular  membrane,  it  mud  be  equally  exten- 
five  with  that  membrane  itfelf,  and  therefore  may 
be  faid  to  pervade  almofl;  the  whole  body.  Hence 
this  may  be  called,  with  perhaps  fufficient  propri- 
ety, the  vis  celluhfa. 

§  44- 
Another  of  the  vital  energies  is,  the  irritability 
of  Hallcr,  which  refides  in  mufcular  fibres  only, 
and  may  therefore  be  called  the  vis  mufcularis* 
It  manifefts  itfelf  by  a  very  fingular,  ofcillatory 
and  tremulous  motion,  eafily  diftinguifhed  from 
limple  contraction,  by  its  being  more  readily  ex- 
cited to  action  on  the  application  of  any  acrid  fti- 
mulus. 

4  §  45- 


OF  THE  VITAL  ENERGIES.  33 

§  45- 
The  third  is  fenfibility,  which  refides  folely  in 
the  nervous  medulla,  communicating  with  the  fen- 
forium,  called  therefore  vis  nervea  ;  when  any 
part  endowed  with  this  property  is  acted  on  by 
irritating  ftimuli,  an  impreflion  is  immediately 
made  on  the  fenforium. 

§46. 

The  three  foregoing  may  be,  with  propriety, 
confidered  as  common  or  general  vital  energies  ; 
becaufe  they  exift,  more  or  lefs,  in  almoft  all,  or 
at  lead  in  a  great  many,  parts  of  the  body,  which 
the  ancients  called  therefore  Jimilarcs,  i.  e.  parts 
of  a  fimilar  nature. 

§  47- 
But  befides  the  foregoing,  there  exifts  alfo  a 
fourth  energy  worthy  of  our  confideration,  namely, 
the  vita  propria,  or  fpecijic  life;  under  which  deno- 
mination I  mean  to  arrange  fuch  powers  as  belong 
to  certain  particular  parts  of  the  body,  deftined  for 
the  performance  of  peculiar  functions,  and  which 
cannot  with  any  propriety  be  referred  to  either  of 
the  claffes  of  coimnon  energies,  formerly  mentioned. 

Inferring  fyntheticaily,    or    a  priori,  as  it  is 

termed,  it  is  not  repugnant  to  found  induction  to 

conclude,  that  parts  differing  from  all  others  in 

vol.  1.  C  texture, 


34  OF  THE  VITAL  ENERGIES. 

texture,  in  arrangement,  and  in  peculiarity  of 
function,  mud  alfo  be  furnifhed  by  nature  with 
peculiar  properties  and  powers,  adapted  to  the 
performance  of  fuch  fpecific  action. 

But  reafoning  analytically,  or  a  pojferiori,  we 
are  likewife  taught  by  accurate  obiervations  made 
on  nature  herfelf,  that  there  are  certain  parts  of 
the  body,  particularly  fome  of  the  vifcera,  which 
perform  motions  fo  very  Angular,  as  cannot  by 
any  means  be  fuppofed  to  arife  from  either  one  or 
other  of  the  common  energies,  of  which  we  have 
already  fpoken,  but  mud  be  referred  to  a  vita 
propria,  or  fpecific  energies  of  their  own. 

Inftances  of  fuch  figularity  of  action  we  have  in 
the  motions  of  the  iris  ;  the  erection  of  the  papilla 
in  the  breafts  of  females  ;  the  moiions  of  the  fim- 
bria: of  the  fallopian  tubes  ;  the  action  of  the 
placenta  ;  the  action  of  the  uterus  in  parturition  ; 
the  defcent  of  the  teftes  in  the  male  foetus ;  and, 
if  I  am  not  deceived,  in  a  great  part,  if  not  in  the 
whole  of  the  procefs  of  fecretion. 

§  48. 

The  fifth  and  lafl  energy  which  claims  our  at- 
tention is,  the  nifus  format  ivus,  or  formative  pro- 
penfity,  which  mould  be  coniidered  as  the  efficient 
caufe  of  the  whole  procefs  of  generation  (taken  in 

fo 


OF  THE  VITAL  ENERGIES.  35 

fo  extenfive  a  latitude  as  to  include  both  nutrition 
and  re-produclion  as  modifications  of  itfelf).  In 
confequence  of  this  propenfity,  the  matter  of  the 
animal  fyflem,  whether  appropriated  to  generation 
or  nutrition,  being  lodged  in  the  places  deftined 
for  its  reception,  and  having  acquired  fufficient  af- 
fimilation  and  m.uurity,  affumes  forthwith  its  due 
arrangement  and  figure,  and  enters  into  the  com- 
pofition  of  thofe  p  trts  which  are  afterwards  fur- 
nifhed  and  enlivened  either  with  the  whole  or 
part  of  the  energies  we  have,  already  enumerated, 
viz.  contractility,  irritability,  fenjibility,  or  finally 
fpecijic  life. 

§  49- 

Of  this  nifus  formativus,  or  formative  propen- 
fity, more  will  be  faid  when  we  come  to  treat  of 
the  proeefs  of  generation. 

Irritability  will  be  more  fully  confidered  when 
on  the  fubject  of  mufcular  motion. 

The  fubjecT:  of  fenfibiliiy  will  be  again  refumed 
when  we  come  to  confider  the  action  of  the  ner- 
vous fyflem. 

Of  the  vita  propria,  or  fpecific  life,  we  will 
every  where  treat,  when  the  fubjecl:  under  confi- 
deration  may  render  it  proper. 

C  2  But 


3<5  OF  THE  VITAL  ENERGIES. 

But  with  refpcct  to  contradility,  the  prefenr 
is  a  very  fuitable  place  to  offer  on  it  a  few  addi- 
tional and  particular  obfervations. 

§  .'O. 
I  have  already  faid  that  this  energy  pervades 
almoft  the  whole  body,  at  lead,  that  its  extent  is 
commenfurate    with    the    extent    of   the    cellular 
membrane. 

In  the  firfl  place,  therefore,  it  refides  in  all 
fuch  pans  as  confift  of  compacted  cellular  fub- 
ftance,  of  which  the  different  membranes  of  the 
body  ferve  as  examples.  That  thefe  poffefs  con- 
tractility will  not  be  denied  by  any  one  who  re- 
flects on  the  conftridtion  of  the  dartos  tunic  >  or 
who  calls  to  mind  the  fpafms  of  the  fkin,  or  of 
the  peritoneum,  which  alone  appears  fometimes 
to  incarcerate  and  flrangle  the  inteftines  in  cafes 
of  hernia. 

Further,  It  alfo  exifts  in  fuch  vifcera  as  are 
compofed  chiefly  of  this  kind  of  membrane  ;  of 
this  defcription  are  the  lungs,  the  external  fuper- 
ficies  of  which  is  highly  contractile,  as  I  have 
lately  learned  from  frequently  puncturing  and  irri- 
tating them  in  a  living  ft  ate  j  but  I  have  not  found 
them  pofTeffed  of  any  real  irritability,  as  has  been 
lately  aliened  by  Varnier. 

Even 


OF  THE  VITAL  ENERGIES.  37 

Even  the  bones  themfelves  do  not  appear  to  be 
entirely  deftitute  of  contractility,  as  we  learn,  not 
only  from  the  alveoli,  which  are  well  known  to 
become  narrower  after  the  extraction  or  lofs  of 
the  teeth,  but  alfo  from  the  morbid  affection  term- 
ed necrofis  (/'.  e.  mortification),  from  which  it  ap- 
pears, that  after  a  lifelefs  part  of  bone  is  quite  re- 
moved, the  new  production  of  bene,  by  which 
the  vitiated  part  was  before  furrounded,  contracts 
itfelf  very  gradually,  almoft  to  the  natural  thick- 
nefs  and  former  figure  of  the  part. 

But  as  we  cbferved  on  a  former  occallon, 
that  the  vitreous  fubftance  of  the  teeth  was  quite 
deftitute  of  cellular  membrane,  fo  it  appears  to 
me  probable,  that  it  is  entirely  deftitute  of  con- 
tractility alfo,  becaufe^  when  a  part  of  it  is  either 
confumed  by  a  caries,  or  broken  off  by  accident, 
the  remaining  portions  or  fides  are  not  approxi- 
mated to  each  other,  as  we  have  already  faid  takes 
place  in  the  alveoli,  but  an  irreparable  hiatus  or 
chaftn  continues  without  a  iliadow  of  diminution. 

§  5'- 

This  very  power  of  contraction,  poffeffed  by  the 
cellular  membrane,  iliould  be  ranked  among  the 
primary  and  leading  fecurities  or  fupports  of  firm- 
nefs  and  health  ;  and  to  it  (hould  be  referred  that 
tone  of  parts,  fo  highly  and  favourably  fpoken  of 

C  3  by 


3 8  OF  THE  VITAL  ENERGIES. 

by  the  acute  and  ingenious  Stahl.  To  advance 
one  argument  in  favour  of  the  foregoing  pofition, 
from  many  which  might  be  adduced,  it  is  the  cel- 
lular fubftance  which,  in  a  healthy  fubject,  ab- 
forbs,  afrer  the  manner  of  a  fponge  the  aqueous 
liquid,  of  which  we  have  already  fpoken,  and  by 
means  of  its  contractility  propels  it  forward  into 
the  lymphatic  veflels :  on  the  contrary,  in  a  dif- 
eafed  flare,  being  deprived  of  its  proper  tone,  and 
reduced  to  an  atcnic  condition,  it  becomes  op- 
prefled  and  diftended  with  a  load  of  water,  and 
thus  gives  rife  to  cedema  and  other  cachectic 
fymptoms. 

§  s* 

Finally,  from  the  univerfal  prevalence  of  con- 
tractility throughout  the  whole  body,  we  may 
plainly  infer  its  influence  and  contagious  effect,  as 
it  were,  on  the  other  vital  energies  ;  and  alfo  from 
its  infinitude  of  modifications  and  degrees  in  dif- 
ferent men,  we  learn  its  highly  influential  part  in 
the  conftitution  of  both  the  proper  health  and  pe- 
culiar temperament  of  each  individual. 


SECT. 


OF  SOUND  HEALTH.  39 

SECT.    V. 
OF  SOUND  HEALTH,  AND  OF  THE  NATURE  OF  MAM. 

§    S3' 

THOSE  three  fubjefts  (§  i.)  in  the 
eonfideration  of  which  we  have  been  hitherto  en- 
gaged, perpetually  act  and  re-act  on  each  other  in 
the  living  human  body.  The  fluids,  for  example, 
aft  by  their  ftimulus  on  the  fclids ;  while  thefe 
again,  in  confequence  of  their  vital  energy,  are 
fitted  and  prepared  both  to  receive  the  action  of 
the  flimulating  fluids,  and  to  re-act  on  them  in 
turn.  In  a  found  and  healthy  fubject,  this  whole 
routine  of  action  and  re-action,  correfponds  with 
fuch  exactnefs  and  definitude,  as  to  conftitute  a 
perfect  and  harmonious  equilibrium. 

§   54- 
There  further  exifts  in  the  living  fyflern  a  won- 
derful confent  of  parts,  even  the  mod  remote ; 
this  confent  is  derived  not  from  one,  but  feems  to 
owe  its  origin  to  different  fources. 

One  of  thofe  fources  refides  in  the  nerves,  de- 
pending as  well  on  the  aftonifliing  net-like  anaflo- 
mofes,  formed  by  their  numerous  branches,  as  on 
the  intricate  nature  of  their  plexus  and  ganglia  ; 
C  4  by 


4o  OF  SOUND  HEALTH. 

by  the  medium  of  which,  the  impulfe  of  ftimuli 
being  communicated  to  the  fenforium,  may  from 
thence  re-a£l  on  parts  more  remote. 

Another  fource  of  this  wonderful  confent  mud 
be  referred  to  the  different  veffels  of  the  fyftem, 
as  well  the  fanguiferous  as  the  lymphatic. 

Another,  again,  arifes  from  a  certain  fimilitudc 
of  ftructure,  giving  origin  to  what  may  be  called 
a  native  fympathy. 

The  cellular  membrane,  which,  as  has  been  al- 
ready obferved,  appears  to  conftitute  a  common 
bond  of  union  to  the  whole  body,  may  be  readily 
conceived  to  poifefs  a  very  ftriking  and  powerful 
influence  in  promoting  the  confent  of  diftant  parts. 

§  SS- 
Finally,  to  this  head  belongs  what  is  juftly  ef- 
teemed  one  of  the  greateft  myfteries  of  nature, 
namely,  the  connection  of  the  mind  with  the 
body,  and  the  diverfified  and  aftonifhing  power  of 
the  one  over  the  other.  As  this  fubject  will  be 
again  refumed,  and  treated  more  fully  in  another 
place,  it  will  be  fufficient  on  the  prefent  occafion 
briefly  to  obferve,  that  befides  the  obvious  power 
of  the  will  over  mod  of  the  mufcles,  there  are 
alfo  other  faculties  which  exert  their  influence  on 

the 


OF  SOUND  HEALTH.  41 

the  body,  even  without  the  concurrence  or  aid  of 
the  will. 


Of  this  defcription  are  thofe  blind  and  purely- 
animal  inftinfts  of  our  nature  ;  fuch,  for  example, 
as  that  which  excites  to  the  gratification  of  vene- 
real enjoyments. 

Further,  the  body  is  greatly  under  the  influence 
of  the  internal  fenfcs,  more  efpecially  of  the  ima- 
gination, and  thofe  pafiions  of  the  mind  which  it 
contributes  to  excite. 

Finally,  it  is  by  the  interpofition,  and  through 
the  medium  of  thefe,  that  a  communication  and 
reciprocal  influence  are  preferved  between  the 
powers  of  the  body,  and  the  more  exalted  facul- 
ties of  the  mind. 

§  56. 

By  this  diverfified  confent  of  the  folids,  of  the 
fluids,  and  of  the  vital  energies  (§  53.),  by  this 
fympathy  of  parts  (§  54.),  and  by  this  intimate 
connection  between  the  mind  and  the  body, 
(S  55-)i  life  and  health  are  preferved  in  vigour  j 
yet  not  always  exifling  in  the  fame,  but  in  widely 
different  degrees  of  perfection  and  energy. 

§  57- 


42  OF  SOUND  HEALTH. 

§  57- 

Between  the  two  extremes  of  life  there  exift 
different  grades,  of  which  one  is  called  vita  max- 
ima, or  perfect  life  j  the  other  vita  minima,  or  im- 
perfect life. 

Life  is  faid  to  be  perfcel  in  the  flower  of  age, 
when  the  functions  of  the  body  have  reached  that 
pinnacle  of  perfection,  called  by  the  Greeks  acme ; 
this  might  alfo  be  denominated  the  athletic  Jlaie. 

Life,  on  the  other  hand,  is  faid  to  be  imperfeel 
when  the  functions  are  performed  with  lefs  vi- 
gour ;  although  their  perfection  may  be  the  mod 
confummate,  when  the  fituation  of  the  f&bjeft,  and 
its  mode  of  exigence,  are  taken  into  confedera- 
tion :  thus  life  is  imperfect  in  a  fcetits  in  utcro, 
and  that  in  proportion  as  the  fcetus  is  tender  and 
young.  Finally,  life  is  lefs  perfect  in  the  Jlecping 
than  in  the  waking  ftate  ;  lefs  perfect  alfo  in  a 
fubject  advanced  in  years,  than  in  one  balking  in 
the  meridian  blaze  of  manhood. 

§  5«- 

The  varieties  in  point  of  health  are  no  lefs  nu- 
merous and  confiderable  :  there  is  indeed  a  cer- 
tain flate  of  health  which  may  be  faid  to  be  pecu- 
liar to  each  individual.      Such  perfons  as  we  fup- 

pofe 


OF  SOUND  HEALTH.  43 

pofe  to  be  in  the  enjoyment  of  the  mofl  complete 
health,  differ,  notwithstanding  furprifingly  from 
each  other,  as  well  in  confequence  of  a  difference 
in  the  conftitution  of  the  blood,  as  of  a  diverfity 
of  tone,  and  of  the  other  vital  energies ;  hence 
different  individuals  are  fo  differently  affected  by 
the  fame  ftimuli  acting  on  their  bodies.  Perhaps 
each  individual  may  poffefs  peculiar  idiofyncra- 
fies,  though  fo  very  inconfiderable  as  to  be  fcarce- 
ly  obfervable :  the  influence  of  cuflom  is  fo  pow- 
erful, as  to  create,  in  different  fuhjects,  an  intole- 
rance of  different  imprefftons,  though  in  them- 
felves  quite  innocent ;  it  alfo  produces  a  facility  of 
bearing,  and  finally  creates  a  defire  for,  fuch 
things  as  appeared  at  firft  both  unnatural  and  dif- 
agreeable. 

§  59- 
This  appears  to  be  the  very  hinge  on  which  re- 
volves the  nature  and  variety  of  temperaments,  fo 
frequently  the  fubjects  of  phyfiological  difcufion. 
The  conftitution  of  the  temperaments  depends,  not 
only  on  the  proportion  and  mixture  of  the  confti- 
tuent  parts  of  the  blood  (§  22.),  but  alfo  on  the 
peculiar  vigour  of  the  vital  energies  already  treat- 
ed of ;   and  likewife  on  the  confequent  variety  in 
the  mode  of  the  reciprocal  action  and  re- action  of 
the  body  and  mind  on  each  other.      From  this 
combination  and  concurrence  nrifes  that  peculia- 
rity 


44  OF  SOUND  HEALTH. 

rity  of  fenfation  to  the  impreffions  of  ftimuli  ;  and 
alfo  that  lingular  power  of  performing  motions 
with  greater  or  lcfs  facility. 

_  §  60. 
Hence  the  varieties  of  temperaments  are  lite- 
rally infinite,  and  can  never  be  reduced  to  any 
certain  and  definite  clafTes.  But  as  it  has  been 
the  pleafure  of  phyfiologifts  to  arrange  them  un- 
der certain  heads,  for  the  fake  of  regularity,  w^ 
may  with  fufHcient  propriety  give  our  aflent  ro  the 
common  mode  of  arrangement,  by  which  they 
have  been  reduced  to  four  orders^  namely,  the 
phlegmatic,  the  fanguineous,  the  choleric,  and  the 
melancholic. 

§  6u 

For  although  Galen  erected  this  divifion  on  an 
abfurd  foundation,  falfely  fuppofed  to  be  derived 
from  the  nature  and  constituent  parts  of  the 
blood,  yet  if  this  erroneous  foundation  be  kept 
entirely  out  of  view,  the  divifion  appears  in  other 
refpe&s  fo  confonant  to  nature,  that  the  different 
temperaments  of  all  men  generally,  and  of  every 
individual  in  the  different  periods  of  life,  may  be 
with  propriety  referred  to  one  or  other  of  thefe 
four  leading  claffes.  Thus,  in  the  tender  age  of 
infancy  the  phlegmatic  temperament  chiefly  pre- 
vails. This  in  youth  is  exchanged  for  the  fan- 
guineous. 


OF  SOUND  HEALTH.  45 

guineous.  The  choleric  marks  the  period  of  man- 
hood. And  the  melancholic  is  the  temperament 
of  old  age. 

But,  as  has  been  already  obferved,  the  variety 
in  the  exifting  degrees  of  the  fame,  and  in  the 
mixtures  of  different  temperaments,  is  fo  un- 
bounded, as  to  afford  an  open  and  a  very  exten- 
five  field  of  fpeculation  to  fuch  as  wouM  with  to 
amufe  themfelves  with  tracing  out,  and  eftablifh- 
ing,  on  this  fubjecl:,  more  minute  combinations,  or 
divifions  and  orders. 

§  62. 

This  whole  collective  affemblage  of  all  the  fa- 
culties and  laws  hitherto  mentioned,  by  which  the 
functions  of  the  human  body  are  performed  and 
regulated  from  the  opening,  to  the  clofing  pulfc 
of  life,  are  called  human  nature^  or  the  nature  of 
man;  from  whence  arofe  the  name  of  phyjiology, 
the  fcience  now  under  our  immediate  confidcration. 

§  63- 

Thofe  functions  of  the  body  may  be  themfelves 
properly  enough  divided  into  four  claries  ;  which 
divifion,  although  not  entirely  free  from  exception, 
nor  perfectly  conformable  to  nature,  may  never- 
thelefs  be  aptly  enough  retained  a3  a  ufeful  afTift- 
ant  to  the  memory. 

I.  The 


4<S  OF  SOUND  HEALTH. 

I.  The  firft  clafs  of  this  divifion  embraces  the 
vital  f unci  ions,  fo  called  becaufe  their  mediant 
and  unmolefted  action,  is  more  efpecially  and  ef- 
fentially  neceffary  to  the  continuance  of  life.  To 
this  clafs  belong  the  circulation  of  the  blood,  and 
after  birth  the  procefs  of  refpiration. 

II.  The  fecond  clafs  embraces  the  animal  func- 
tions;  thefe  ferve  to  diftinguifh  annuals  from  or- 
ganifed  bodies  belonging  to  the  vegetable  king- 
dom *.    This  clafs  in  man  includes  the  connection 

*  I  lament  it  as  a  ferious  misfortune  to  the  fcience  of  na- 
tural hijiory,  that  his  final  object  did  not  call  on  the  very 
learned  and  ingenious  profellbr  to  be  more  explicit  and  mi- 
nute on  that  clafs  of  functions  denominated  the  animal.  He 
has  told  us  in  terms  very  general  and  definite,  that  they  are 
filch  as  ferve  to  constitute  the  great  barrier  of  distinction  be- 
tween animal  and  vegetable  bodies.  I  am  forry  that  neither 
the  object  nor  extent  of  an  elementary  work  permitted  him  to 
defcend  to  a  more  minute  fpec'-fication  of  thof;  characterises, 
in  which  the  difference  between  animals  and  vegetables  more 
immediately  conlifts.  Few  points  of  investigation  can  be 
propofed  which  have  given  rife  to  a  greater  diverfity  of  opi- 
nion, than  that  which  refpects  the  difference  between  thefe 
two  claffes  of  natural  bodies  ;  and  fewer  ftill  perhaps  can  be 
advanced,  with  regard  to  which  philofophers,  even  in  the  pre- 
fent  imperfect  ftate  of  phyfical  fcience,  Should  more  unani- 
mously agree.  Be  this  later  pofition,  however,  true  or  falie, 
1  have  ;.lways  been  led  to  confider  the  Strangely  diveriified, 
and  even  contradictory  opinions,  entertained  by  naturalifts 
refpe&ing  the  difference  between  animals  and  vegetables,  as 

fo 


OF  SOUND  HEALTH.  47 

of  the  mind  with  the  body,  but  it  regards  more 
efpecially  fenfation,  and  mufcular  motion. 

fo  many  unanfwerable  teftimonies  of  the  equivocality  of  the 
whole.  The  difcovery  therefore  of  an  exclufive  line  of  dif- 
tindYton  between  the  animal  and  vegetable  kingdoms,  (if  in- 
deed thefupreme  author  and  arbiter  of  nature  permits  fuch  a 
line  to  exift)  muft  ftill  be  confidered  as  a  peculiar  dijideratum 
in  the  fcience  of  natural  hiftory. 

From  all  my  {peculations  on  this  interefting  fubjecT:  (and 
it  is  with  me  a  favourite  object  of  purfuit)  I  am  firmly  of 
opinion,  that  there  exifts  no  incommunicable  characterillic, 
and  I  will  venture  to  add,  no  congregation  of  characteriftics, 
which  ferve  to  conflitute  a  complete  partition-veil  between 
the  animal  and  vegetable  kingdoms.  The  numerous  and 
highly  diverilfied  fubje&s  of  thefe  two  important  kingdoms 
of  life,  appear  to  be  nothing  elfe  than  different  individuals  of 
one  extenfive  family,  defcended  from  a  common  parent,  and 
exhibiting  the  mod  unequivocal  teftimonies  of  their  kindred 
nature.  Like  the  delicate  tints  of  light  and  fhade  in  a  well  fin- 
ifhed  picture,  they  fo  gradually  intermingle,  and  run  into  each 
other  fo  infenfibly,  that  it  is  literally  impoffible  to  fay  with 
definitude,  where  the  one  terminates  and  the  other  begins 

All  refearches  therefore  after  an  exclufively  difiinctive  cha- 
racteristic between  vegetables  and  animals,  appear  to  me  equal- 
ly irrational  and  vifionary  with  the  late  enthufiadic  purfuits  of 
the  deluded  alchemifts,  after  the  philofopher's  ftone,  or  their 
more  chimerical  refearches  after  their  flattering  panacea. 
Why  then  fliould  man,  prefumptucus  man  !  attempt  the  ef- 
tablifhment  of  an  eiTential  dillinction  between  phyfical  bodies 
where  wiler  nature  acknowledges  none  ! 

2  HI. 


48  MOTION  OF  THE  BLOOD. 

III.  The  natural  functions  conftitute  the  third 
clafs.  Thefe  are  fubfervient  to  the  nourifhment 
of  the  body. 

IV.  The  fourth  and  laft  clafs  confifts  of  the  ge- 
nital functions,  which  are  deftined  for,  and  employ- 
ed in  the  propagation  of  the  fpecies. 

Let  us  now  confider  each  clafs  of  functions  in 
order,  beginning  with  the  vital. 


SECT.     VI. 
OF  THE  MOTION  OF  THE  BLOOD  IN  GENERAL. 

§  64- 

±  HE  blood  as  we  have  already  feen,  af- 
fords the  primary  origin  to  the  principal  parts  of 
the  body,  and  continues  afterwards  to  convey  to 
them  uniform  and  perpetual  fupplies  of  nourifh- 
ment, and  ought  therefore,  with  a  very  few  ex- 
ceptions (§  5.)  to  be  diftributed  far  and  wide, 
through  even  the  moft  fubtle  and  diftant  receffes 
of  the  whole  body.  That  fuch  a  minute  diftribu- 
tion  actually  takes  place,  we  learn  not  only  from 
a  fine  injection  of  the  vefTels,  but  alfo  from  every 
day's  experience,  from  which  it  appears  that  very 

1  few 


MOTION  OF  THE  BLOOD.  49 

few  parts  of  the  body  can  be  pun&ured  with  the 
point  of  the  fmalleft  pin  without  the  occurrence 
of  a  greater  or  lefs  hemorrhagy. 

§  6*- 

This  vital  liquid  does  not,  as  was  the  opinion 
of  the  ancients,  flow  and  ebb  like  the  waves  of 
Euripus  *,  through  channels  of  the  fame  nature 
and  order,  but  is  fo  moved  onward  in  an  orbit, 
or  circulates,  as  they  exprefs  it,  in  fuch  a  manner, 
as  to  be  carried  from  the  heart,  by  means  of  the 
arteries,  to  every  part  of  the  body  ;  and  being 
there  taken  up  by  the  veins,  conveyed  back  again 
by  them  to  the  fame  original  fountain,  the.  heart* 

§  66. 
After  a  few,   and  thofe  very  indefinite,  expref- 
fions  j-  of  his  predeccfTors,  William  Harvey  efta- 

*  A  narrow  arm  of  the  fea,  extending  between  Bocotia  and 
Euboea,  faid  to  ebb  and  flow  feven  times  during  each  diurnal 
revolution  of  the  earth,  or  each  term  of  24  hours.  In  this 
extraordinary  portion  of  fea,  Ariftotle,  that  celebrated  anci- 
ent philoiopher,  is  falfely  reported  to  have  drowned  hirnfelf, 
becaufe  he  was  not  able  to  develope  the  caufe  of  the  conflant 
flux  and  reflux  of  its  waters.  C.     C. 

f  The  unfortunate  Serveius,  and  that  truly  illuftrious  cha- 
rafter  Andr.  Cafalpinus,  appear  to  have  advanced  nearer  to  a 
true  knowledge  of  the  genuine  circulation  of  the  blood,  than 
any  of  the  other  phyfiological  writers  who  are  conjrnordy 
enumerated  in  the  fame  clafs. 

rot   i.  D  It 


50  MOTiON  OF  THE  BLOOD. 

blifhed,  in  a  manner  tolerably  conclnfive,  the  cir- 
culation of  the  blood,  in  a  fmall  but  immortal 
work  publifhed  in  the  year  1628. 

In  procefs  of  time,  however,  every  fliadow  of 
doubt  en  this  fubjeft  was  removed.  This  was 
effected  chiefly  by  frequent  rccourfe  to  adtual  and 
fimple  obfervations  with  the  microfcope ;  but  in 
part  alfo  by  injections  of  wax  and  other  fubftances 
into  the  arteries,  which  were  feen  paffing  again 
to  the  heart  by  the  route  of  the  veins  ;  and,  fur- 
ther, by  the  elegant  and  fublime  experiment  of 

It  may  not  be  improper  on  the  prefent  occafion  to  advert 
to  a  remarkable  claufe  in  the  writings  of  Servetus,  contained 
in  a  phyfiological  dilfertation,  which  he  included  in  his  cele- 
brated and  very  fcarce  work,  that  occafioned  the  death  cf  its 
illuftrious  author.  The  work  is  entitled  "  Reflitutio  Chrifti- 
anifmi,"  &c.  (Viennx  Allobrog.)  1553-8.  The  differ  cation 
particularly  alluded  to,  is  contained  in  the  fifth  book  of  the 
abovementioned  work,  "  de  trlnitate  divina,  in  quo  ag'itur  de 
fpiritu  fancto,"  in  which  we  are  presented  with  the  following 
words,  "  Vitalis  e/t  fp'tr'itus  qui  per  anajlomofes  ab  arttriis  com- 
muntcatur  vcnist  in  quibus  dicilur  naturalist* 

But  from  the  memorable  problem  of  Ccefalpinus,  "  de  ve- 
nit  ultra  vinculum  tumeftentibus,  non  citra,"  it  appears  obvious 
as  the  blaze  of  day,  that  that  truly  illuftrious  phyfiologift 
trod  on  the  very  confines  of  a  complete  knowledge  cf  the 
circulation  of  the  blood.  See  his  "Qmcftionum  medica- 
rum,"  L.  II.  quseft.  17.  page  234. 

transfufincr 


MOTION  OF  THE  BLOOD.  51 

transfufing  the  blood  of  one  living  aiiiraa]  into 
another,  or  into  a  human  fubject  ;  as  alfo  by  vari- 
ous other  experiments  which  may  be  performed 
on  animals  in  a  living  (late. 

§  67. 
What  fliould  be  efteemed  the  definite  ftandafd 
of  the  celerity  of  this  motion,  in  a  healthy  human 
fubjecl,  we  are  not  well  able  to  determine.  In 
this  refpecl  there  is  not  only  a  difference  between 
one  fubjecl  and  another,  but  there  alfo  occurs  a 
great  variety  relating  to  this  point,  arifing  from 
the  difference  of  ages  :  there  indeed  exifts  a  dif- 
ference in  the  celerity  of  the  blood's  motion,  even 
in  the  different  parts  of  the  fame  body. 

Finally,  the  venous  blood  appears  to  glide  on 
more  flowly  than  the  arterial  ;  and  when  flowing 
through  the  trunks  of  veffels,  its  motion  is  more 
rapid  than  when  palling  their  fmaller  ramifica- 
tions. Former  phyfiologifls,  however,  have  not- 
withftanding  exaggerated  thefe  feveral  diverfities, 
in  the  celerity  of  the  blood's  motion,  beyond  their 
natural  magnitude. 

The  common  conclufion,  however,  on  this  fub- 

jeft  is,  that  the  blood,  flowing  through  the  aorta 

with  its  mean  velocity,  paffes  over  a  diftance  of 

about  eight  inches  during  the  fpace  of  one  pulfa- 

D  2  tion  ; 


52  MOTION  OF  THE  BLOOD. 

tion  ;  at  which  rate  it  would  travel  about  fifty  fee: 
in  the  fird  minute  of  time. 

§  68. 

The  globules  of  the  cruor  appear  to  revolve  on 
their  axes  or  centres  of  motion  ;  and  it  is  faid  that 
the  fame  are  propelled  forward  with  greater  velo- 
city than  the  other  conflituent  parts  of  the  blood. 
I  know  not  whether  this  conclufion  be  drawn 
from  actual  experiment,  or  whether  it  be  only  an 
inference  from  an  abfurd  application  of  the  com- 
mon laws  of  hydraulics  to  the  circulation  of  the 
blood  :  I  call  the  application  abfurd,  becaufe  it  is 
certainly  the  very  fummit  of  folly,  to  attempt  to 
account  for  that  motion  of  a  vital  flu'd,  by  which 
it  is  carried  through  the  living  canals  of  an  ani- 
mated fyftem,  on  the  purely  mechanical  principles 
by  which  water  is  forced  through  hydraulic  ma- 
chines.— As  to  myfelf,  I  muft  acknowledge  I  have 
never  been  fo  fortunate  as  to  be  favoured  with 
a  view  of  this  prerogative  or  preceffion  of  the 
globules. 

§  69. 
I  am  fully  perfuaded,  that  thofe  globules  only 
glide  forward,  fufpended  or  fwimming  in  the  fluid 
formed  by  the  other  conflituent  parts  of  the  blood, 
but  that  they  do  not  at  the  fame  time  rotate  on 
their   own  axes   at  all.     To   conclude,  it   is  not 

fully 


MOTION  OF  THE  BLOOD.  53 

fully  and  clearly  afcertained,  that  the  blood,  be- 
fides  its  progreffive  motion,  of  which  we  are  now 
fpeaking,  is  alfo  fubje&ed  to  one  of  a  different 
kind,  called  an  inteftine  motion  ;  although  there 
can  be  no  doubt,  but  that  the  elementary  parts  of 
the  blood  may  be  occafionally  affected  in  their 
arrangement  and  combination,  when  they  are 
tumultuoufly  ■unrated  in  confequence  of  the  im- 
menfely  varied  directions.,  the  minute  divifions  and 
numerous  anaftomofes  of  the  reikis  through  which 
they  pafs. 

§  7°- 
Thus  much  we  thought  proper  to  advance  on 
the  motion  of  the  blood  in  general.  Previoufly 
to  our  entering  on  a  more  dofe  and  minute  con- 
fideration  of  this  fubjecl,  we  think  it  beft  to  treat 
of  the  vclTels  in  which  the  blood  is  contained,  and 
alfo  to  confider  with  attention  the  energies,  by 
which  thefe  veiTels  are  animated,  and  fitted  both 
to  receive  and  again  propel  the  blood. 


B  3  SECT. 


U  OF  THE  ARTERIES. 

SECT.    VII. 

OF  THE  ARTERIES. 

§  71- 

J.  HE  veffcls  which  receive  the  blood 
immediately  from  the  heart,  and  convey  it  to  all 
the  different  and  minute  parts  of  the  body,  are 

called  arteries* 

In  their  collective  or  aggregate  dimcnfions,  they 
are  lefs  capacious  than  the  veins;  but  their  texture 
is  far  more  folid,  more  compact,  very  elaftic,  and, 
as  appears,  from  the  experiments  of  Wintringham, 
remarkably  ftrong. 

§  7'2- 
They  are  compofed  of  three  membranous  ftrata, 

or  coats. 

I.  Of  an  external,  which  Haller  called  a  true 
cellular  coat,  Albinus  a  nervous,  Vefalius  a  carti- 
laginous, others  a  tendinous,  &c.  It  confifts  of 
CQndenfed  cellular  membrane,  externally  more  lax, 
but  becoming  by  degrees  more  compact,  as  you 
advance  nearer  to  its  internal  furface,  where  it 
i:  overfpn  ad  with  numerous  fmall  blood  veffels. 

To 


OF  THE  ARTERTES.  55 

To  this  coat  the  artery  appears  to  be  chiefly  in- 
debted for  its  tone  and  elasticity. 

II.  The  fecond  or  middle  ftratum,  is  compofed 
of  tranfverfe  fibres,  afluming  a  lunated  or  falciform 
figure  and  dire&ion  ;  its  fubflance  has  a  flefhy  ap- 
pearance, from  whence  it  has  been  called  the 
mufcular  coat,  and  in  it  the  vital  energy  of  the 
arteries  appears  in  a  very  particular  manner,  to 
refide. 

III.  The  laft  and  mod  internal  coat,  is  a  mem- 
brane of  an  extremely  fmooth  and  polifhed  furface, 
which  ferves  as  a  lining  to  the  cavity  of  the  artery. 

In  the  trunks  and  larger  branches  of  the  arte- 
ries, thele  coats  may  be  diflin&ly  obferved  ;  but 
they  are  lefs  evident  in  the  more  minute  ramifica- 
tions. 

§  73- 
All  the  arterial  branches  in  the  human  body 
take  their  origin  from  either  one  or  the  other  of 
two  leading  trunks. 

The  firjl  of  thefe  trunks  is  the  pulmonary  artery, 
which,  rifing  from  the  anterior  ventricle  of  thr 
heart,  pafTes  into  the  lungs. 

D  4  The 


5 6  OF  THE  ARTERIES. 

The  fccond  is  the  aorta,  which  rifes  from  the 
pofterior  ventricle  of  the  heart,  and  fhoots  its 
ramifications  into  every  part  of  the  fyftem. 

Thefe  trunks  are  divided  into  branches,  which 
again  undergo  farther  and  more  minute  fubdi- 
viiions. 

§   74- 

An  opinion  has  been  conceived  and  propa* 
gated  as  an  eftablifhed  truth,  that,  throughout 
the  whole  fanguiferous  fyftem,  the  aggregate  capa- 
city of  all  the  branches,  taken  together,  is  fuperior 
to  that  of  the  trunk  from  which  fuch  branches 
dircclly  originate.  I  fear,  however,  that  the  au- 
thors of  this  opinion  have  exprefTed  tbemfelves 
on  this  fubjeel:  in  terms  by  far  too  general,  and 
have  fometimes  even  confounded  the  meafure  of 
the  diameter  of  veffels,  with  that  of  their  nrea.  In 
my  inveftigations  and  inquiries  on  this  fuhjecr,  I 
did  not  truft  to  the  refult  of  a  fingle  experiment, 
nor  did  I  confine  my  experiments  to  veffels  filled 
with  wax,  which,  however  improper,  were  the 
only  kind  ufed  by  fome  celebrated  phyfiologiits, 
in  their  attempts  to  afcenain  the  matter  now  under 
conlideration  ;  but,  as  the  nature  and  importance 
of  the  fubjeel:  evidently  demanded,  I  made  my 
experiments  and  obfervations  on  the  found  and 
rnakered  veffels  of  fubjecls  recently  dead.    I  took, 

for 


OF  THE  ARTERIES.  57 

for  example,  that  namelefs  trunk  from  which  the 
ri^ht  carotid  and  fubclavian  arteries  diverge  as 
branches,  and  alfo  the  brachial  trunk,  together 
with  its  branches,  the  radial  and  cubital  arter'es, 
and  having  formed  a  rectangular  triangle,  from 
the  di. .meter  of  the  trunk  and  the  diameters  of  its 
appended  ramifications,  I  found,  from  the  well 
known  theorem  of  Pythagoras,  that  the  iquare 
of  the  hypothenufe  was  equal  to  the  fum  of  the 
fquares  of  the  bafc  and  perpendicular. 

Indeed,  in  arteries  of  the  (mailed  orders,  Haller 
himfelf  acknowledged  that  the  capacity  of  the 
trunks  is  greater  than  that  of  their  ramifications  ; 
fo  that,  at  lead,  the  common  calculation  does  not 
apply  univerfally,  but,  (if  it  be  indeed  ever  admif- 
fible),  mud  be  reftri&ed  to  a  very  few  orders  of 
vefTels. 

S  75- 

Each  trunk  and  ramification,  feparately  confi- 
dered,  have  been  commonly  believed  to  pofTefs 
a  conical  figure,  the  bafe,  or  that  part  next  to 
the  heart,  being  fuppofed  more  capacious  than 
the  oppofite  extremity.  This  opinion  appears 
however  to  be  hypothetical  :  for,  whoever  will 
take  the  trouble  of  examining  the  arteries  with 
accuracy  and  attention,  will  find  their  figure  to  be 
perfectly  cylindrical :  indeed,  on  the  other  hand, 

there 


5  8  OF  THE  ARTERIES. 

there  are  not  wanting  inftanccs  of  fome  arteries 
which  in  their  progrefs  rather  widen  and  expand, 
fuch,  for  example,  are  the  mammarise  interna?,  or 
internal  rnammaries,  and  even  the  arch  of  the 
aorta  itfelf  is  more  contracted  at  its  bafe  than  at 
its  apex  or  top.  All  arteries,  efpecially  thofe  of 
the  larger  orders,  appear  to  be  a  little  dilated  and 
enlarged,  jufr  before  their  divifion  into  branches. 

§  7& 

The  number  of  orders,  formed  by  the  divifions 
of  the  main  arterial  trunk  into  the  progrellive 
feries  of  uniformly  decreafing  ramifications,  from 
its  firfl  origin  at  the  heart,  to  its  final  termination 
in  the  extreme  capillaries,  cannot  poiTibly  be  uni- 
verfally  afcertained  and  eftablifhed  as  a  general 
and  unvarying  refult.  The  truth  of  this  pofition 
will  be  obvious  to  any  one  who  confiders,  that  in 
the  different  parts  of  the  body,  efpecially  in  the 
vifcera,  the  arteries  are  fubjecl:  to  great  variety 
with  refpect  to  their  divifions  ;  and  that,  on  this 
account,  they  fomctimes  form  more,  fometimes 
fewer  orders  of  vefTels,  previoufly  to  their  fepa- 
ration  into  evanefcent  capillaries. 

Hence  the  disagreement  of  authors  who  have 
attempted  to  amufe  themfelves  with  calculations 
of  this  kind.  Thus,  for  example,  Keil  eflimated 
the  number  of  the  orders  of  arteries  at  fifty,  while 

Haller 


OF  THE  ARTERIES.  $9 

Haller  contended  that  they  amount  to  no  more 
than  twenty. 

S  77- 

After  numerous  divifions  of  this  kind,  and  va- 
rious anaftomofes,  by  which  the  neighbouring 
branches  of  arteries  communicate  with  each  other, 
they  at  length  arrive  at  their  final  terminations, 
which  are  completely  continuous  with,  or  which 
fairly  open  into,  the  origins  of  veins  ;  fo  that, 
(heir  route  being  uninterrupted,  they  are  reflected 
from  extremities  that  can  fcarcely  be  difcerned, 
and  thus  converted  into  thofe  returning  veffels,  by 
which  the  blood,  lately  arterial,  but  now  become 
venous,  is  conveyed  back  again  to  the  heart. 

§  78. 
But  although  this  complete  continuity  of  the 
arteries  and  veins  be  fo  extremely  evident  in  nu- 
merous parts  of  the  body,  as  to  be  obvious  even 
to  the  naked  eye,  yet  it  ilill  remains  a  matter  of 
doubt,  whether  this  be  the  only  and  exclufive 
mode,  in  which  arteries  communicate  with  veins, 
or  whether  there  may  not  be,  at  lead  in  certain 
parts  of  the  fyflern,  an  intermediate  and  parenchy- 
matous fu.bit.ance,  which  receives  the  blood  from 
the  terminations  of  the  arterits,  and  again  depo- 
fits  it  in  the  incipient  mouths  of  the  veins  ? 

There 


Co  OF  THE  ARTERIES. 

There  occur  certain  phenomena,  fuch  for  ex- 
ample, as  erections  of  the  penis,  and  the  common 
phenomenon  of  blufliing,  which  render  the  ex- 
iftence  of  fuch  a  connecting  medium  between 
thofe  two  kinds  of  veffels,  at  lead  not  improbable. 

§  79- 
There  are,  again,  veffels  of  a  nature  evidently 
different  from  thofe  already  fpoken  of,  which  ap- 
pear to  arife  every  where  from  the  fmaller  arte- 
rial branches  ;  thefe  veffels  confift  chiefly  of  two 
kinds,  namely,  the  ferous,  which  are  fo  narrow  as 
not  to  be  able  in  a  healthv  fubject  to  admit  the 
globules  of  the  cruor,  but  only  to  receive  the 
thinner  fluid  or  vehicle  in  which  thofe  globules 
fwira  (§  69.)  ;  and  the  fecrctory,  which  do  not 
appear  to  attract  any  thing  from  the  mafs  of  arte- 
rial blood,  but  fuch  fpecific  fluids  as  are  deftined 
for  fecretion  (§  4.) 

§  80. 

With  regard  to  the  former  kind  of  veffels, 
which  we  denominated  ferous,  it  is  neceffary  to 
obferve,  that  we  do  not  mean  by  them  the  imagi- 
nary orders  of  yellow  and  of  white  veffels,  fpoken 
of  by  Boerhaave,  which  appear  to  have  been  fan- 
cifully conceived,  in  conformity  to  the  account 
given  by  Lecuwenhoek  of  his  equally  imaginary 
fixfcld  conformation  of  the  globules  of  the  blood  : 

neither 


OF  THE  ARTERIES.  61 

neither  do  we  mean  the  neuro-lymphatic  veffcls 
of  Vieuflen  and  Ferrein,  of  which  thofc  gentle- 
men fuppofed  the  vifcera  to  be  in  a  great  meafure 
compofed  ;  but  which  do  not  indeed  appear  to  be 
any  better  founded  than  the  preceding  conjectures 
of  Boerhaave  and  Leeuwenhoek. 

By  the  ferous  we  mean  thofe  colourlefs  veflfels 
which  are  never  vifible,  unlefs  in  certain  cafes  of 
violent  inflammation,  where  the  impetus  of  the 
blood  is  very  powerful ;  and  indeed  in  fome  parts 
of  the  body,  even  this  energetic  procefs  of  nature 
is  not  of  itfelf  fufhciently  powerful  to  bring  them 
into  view,  unlefs  they  be  dill  farther  dilated  by 
means  of  an  anatomical  fyphon  or  injector  :  of  this 
latter  description  are,  for  example,  the  vefTels  of 
the  cornea,  which  can  fcarcely  ever  be  filled  with 
wax,  unlefs  in  the  dead  bodies  of  fuch  fuhjects  as 
have  died  while  labouring  under  a  violent  inflam- 
mation of  the  eyes. 

§  Si. 

The  fecretory  veflels,  on  the  other  hand,  appear 
to  be  different  from  thofe,  and  belong  chiefly  to 
the  fecreting  vifcera  and  conglomerate  glands  •, 
they  can  alfo  be  traced  by  means  of  a  very  fubtle 
injection,  which,  for  inflance,  when  thrown  with 
force  into  the  artery  of  the  parotid  gland,  flows 
out  and  efcapes  through  the  duel  of  Stenonius. 

But 


61  OF  THE  VEINS. 

But  on  thefe  veffels  we  will  have  a  ftated  oppor- 
tunity of  being  more  pointed  and  particular  in  a 
fubfequent  fcclion. 


SECT.    VIII. 
OF  THE  VEINS  WHICH  CARRY  BLOOD. 

§   82. 

X  HAT  blood,  which,  by  means  of  the 
arteries  has  been  diftributed  throughout  every 
part  of  the  fyftem,  mufl  be  conveyed  back  again 
to  the  heart  through  the  medium  of  the  veins. 

Thefe  veffels  differ  very  widely  from  the  arte- 
ries, both  in  their  functions  and  flruclaire  :  to  this, 
however,  veins  of  the  fmalleft  orders  form  an  ex- 
ception, as  their  ftruclure  does  not  differ  from  that 
of  arteries  of  the  fame  magnitude  in  fo  wide  and 
obvious  a  degree. 

§  S3- 
The  veins  (if  we  except  the  pulmonary  fyftem) 
are  more  capacious  in  their  collective  or  aggregate 
dimenfions  than  the  arteries ;  their  ramifications 
are  alfo  more  numerous  ;  they  are  much  more  ir- 
regular in  their  courfes  and  modes  of  ratifying  j 

their 


OF  THE  VEINS.  6j 

their  texture  is  alfo  much  fofter  than  that  of  the 
arteries  ;  they  are  far  lefs  elaftic,  but  nevertheless 
extremely  tenacious,  and  capable  of  wonderful  ex- 
pa  nfion. 

§  »s- 

Their  coats  are  considerably  thinner  than  thofe 
of  the  arreries ;  whence  the  blood  which  they 
contain  appears  in  fome  meafure  through  them  ; 
they  are  alfo  lefs  numerous,  being  no  more  than 
a  certain. cellular  coverings  fomewhat  refembling 
what  has  been  called  the  nervous  coat  of  the  ar- 
teries, and  an  internal  membrane  of  a  very  exqui- 
fite  polilh,  fimilar  to  that  with  which  the  arteries 
are  lined. 

No  part  of  the  venous  fyilem  is  furnifhed  with 
mufcular  fibres,  except  the  larger  trunks  near  the 
heart. 

§  86. 

In  by  far  the  greater  number  of  the  larger 
veins,  fuch,  for  example,  as  exceed  in  their  dia- 
meter the  twelfth  part  of  an  inch,  this  internal 
membrane  forms,  by  its  foldings,  an  immenfe  num- 
ber of  valves  of  the  moft.  beautiful  ftru&ure,  ex- 
ceedingly pliant  or  moveable,  and  exhibiting  the 
appearance  of  fmall  facks  :  they  are,  for  the  mod 
part,  fimple  and  alone,  frequently  however,  ar- 
1  rataged 


64  OF  THE  VEINS. 

ranged  in  pairs,  and  fometimes  in  riplets ;  and 
are  fo  fituatcd  and  difpofed,  that  the  bottom  of 
the  little  fack  points  to  the  origin  of  the  vein, 
while  its  mouth  or  orifice  opens,  and  is  directed 
towards  the  heart. 

Thofe  fmall  valves  are,  neverthelefs,  wanting  in 
the  veins  of  certain  pans,  as  in  thofe  of  the  ence- 
pha'on,  the  lungs,  Sec.  and  in  the  whole  fyftem  of 
the  vena  potarum. 

§  87. 

The  fmall  ramifications  of  the  veins  (which 
would,  indeed,  with  more  propriety  be  called  their 
radicles  or  little  roots)  form,  by  their  jun&ions, 
larger  branches,  and  thefe  unite  finally  into  fix 
leading  trunks ;  viz.  the  two  vena  cava,  one  cal- 
led the  fupcrior,  the  other  the  inferior,  and  the 
four  trunks  of  the  pulmonary  vein. 

The  vena  portaritm  alone  exhibits  one  pheno- 
menon peculiar  to  itfelf.  The  trunk  of  that  vein, 
on  entering  the  liver  is,  after  the  manner  of  an 
artery,  immediately  divided  into  branches,  the 
extreme  ramifications  of  which  become,  at  length, 
radicles  to  the  inferior  cava,  and  finally  lofe  them- 
felves  in  the  bofom  of  that  trunk. 

1  §  83, 


OF  THE  VEINS.  if 

§  88. 
We  need  not,  on  the  prefent  occafion,  again 
advert  to  the  common,  and  by  far  too  general, 
opinion,  that  the  areas  of  the  branches  are  more 
capacious  than  the  area  of  the  trunk  from  which 
they  rife,  nor  yet  to  that  refpecling  the  conical 
figure  of  fingle  veffels,  as  what  was  faid  on  thofe 
fubjects,  when  treating  of  the  arteries  (§  74,  J$.), 
will  apply  with  fufficient  precifion  to  the  veins. 

There  are  alfo  among  the  veins,  a  few  examples 
of  veffels  being  more  capacious  at  a  more  remote 
distance  from  the  heart ;  fuch,  for  inflance,  is  the 
vena  poplitea,  where  it  pafTes  between  the  condyls 
of  the  os  fcmoris. 

What  has  been  already  faid,  with  regard  to  the 
final  terminations  of  the  arteries  (§  77,  78,  80.), 
may,  by  making  fuch  obvious  and  neceflary 
changes,  as  are  adapted  to  the  different  nature 
and  circuinftances  of  our  fubject,  be  fitly  applied 
to  the  origins  of  the  veins. 


TOL.    I. 


E  SECT.. 


66  OF  THE  HEART. 

SECT.     IX. 

OF    THE    HEART. 

§  89. 

1  HERE  cxifls,  as  we  have  already  had 
occafion  to  obferve  (§  65),  a  two-fold  communi- 
cation between  the  arteries  and  veins:  one,  for 
inftance,  at  the  minute  extremities  of  each  kind  of 
veffels  (§  77)  ;  and  the  other  at  the  heart,  their 
common  fountain,  in  which  the  leading  trunks  of 
the  whole  fanguiferous  fyitem  meet. 

§  9°- 
The  heart  is,  as  it  were,  the  firft.  active  orgafc 
and  moving  fpring  of  the  whole  human  machine, 
as  it  is  by  the  perpetual  and  truly  aftonifhing 
energy  of  this  body,  that  the  mod  important  vital 
function,  namely,  the  circulation  of  the  blood,  it 
performed,  from  fo  early  a  date  of  our  exiftence, 
as  the  fourth  week  after  conception,  down  to  the 
clofing  period  of  tranfient  life. 

§  91- 

This  active  organ,  by  its   alternate  dilatation 
and  contraction,  firft:  receives  and  again  ejects  the 
blood  in  the  following  manner.     Into  the  anterior 
venous  finus,  and  its  appendage,  the  anterior  auri- 
cle 


OF  THE  HEART.  67 

€le  of  the  heart,  the  blood  is  conveyed  from  the 
whole  body,  by  means  of  the  two  vena  cava,  viz. 
the  fuperior  and  inferior,  and  likewife  from  the 
fubftance  of  the  heart  itfelf,  by  means  of  the  coro- 
nary veins,  the  common  orifice  of  which  is  fur- 
nifhed  with  a  valve  of  a  peculiar  ftru&ure ;  and 
from  this  auricle,  it  is  again  conduced  into  the 
correfponding  ventricle  of  the  fame  fide^ 

§  92^ 

From  this  anterior  ventricle  (formerly  called 
the  right  ventricle,  in  conformity  to  the  fituation 
of  the  heart  in  brutes)  the  blood  is  thrown  into 
the  lungs  through  the  pulmonary  artery,  which 
was  called  by  the  ancients  vena  arteriofa;  from 
thence,  by  the  four  pulmonary  veins,  called  in 
former  times  arteria  venofa,  it  is  conduced  into 
a  common  finus,  formed  by  their  conflux,  and 
thence  again  into  the  correfponding  auricle  ;  thefe 
were  once  called  the  left,  but  are  now  more  pro- 
perly named  the  pojlerior,  finus  and  auricle. 

§   93- 
From  the  pofterior  auricle  it  pafTes  on  to  the 

ventricle  of  the  fame  fide,  from  whence  it  is  diftri- 

buted,  by  means  of  the  aorta,  through  the  whole 

arterial  fyftem  appropriated  to  the  other  parts  of 

the  body,  and  by  the  coronary  arteries,  through 

the  fubftance  of  the  heart  itfelf. 

E  2  §'  94. 


63  OF  THE  HEART. 

§    94- 
The  blood  having  palled  from  the  extreme  and 

ultimate  branches  of  the  arterial,  into  the  incipient 

radicles  of  the  venous  fyjlem,  re-enters  the  two 

vena?  cava?,  (while  that  from  the  coronary  arteries 

is  alio  returned  by  veins  of  the  fame  name),  and 

thus  the  whole  collective  volume  refumes  again, 

and  inceffantly  continues,  the  fame  circuitous  route 

already  defcribed. 

§  95- 
This  circular  and  regularly  progrefUve  motion 
of  the  blood  through  the  cavities  of  the  heart,  is 
powerfully  directed,  and  the  regurgitations  of  that 
fluid  are  completely  prevented,  by  means  of  fmall 
valves,  which  furround  and  ferve  as  portals  to  the 
principal  avenues  which  lead  to  the  heart.  Thefe 
valves  are  fituated  on  the  margins,  or  extreme  lips, 
of  the  ventricles  which  are  adjacent  to,  and  look 
towards,  their  correfponding  fmufes,  and  alfo  at 
the  mouths  of  the  two  great  arterial  canals  leading 
out  of  thofe  ventricles. 

§  96. 

Thus  a  fmall  venous  ring  or  tendon,  which 
forms  a  partition  between  the  anterior  finus  and 
ventricle,  defcending  into  the  cavity  of  the  latter, 
feparates  into  three  fmall  valves  of  a  tendinous 
appearance,  each  one  of  which  was  formerly  be- 
lieved to  divide  again  into  three  apices  or  points, 

from 


OF  THE  HEART.  69 

from  whence  they  received  the  name  of  valvules 
trigiochines  or  tricitfpides,  Thefe  valves  are  con* 
netted  at  their  points  to  fiefhy  columns,  common- 
ly called  miifzull  papillarcs. 

§  97- 

In  like  manner  another  fmall  ring  of  the  fame 
kind,  which  constitutes  a  partition  between  the 
pofterior  finus  and  ventricle,  is  alfo  divided  into 
two  fmall  valves,  which,  from  a  certain  fuppofed 
refemblance  to  ^facerdotal  mitre,  have  been  called 
valvule  mitralcs. 

§98. 

At  the  entrance  into  the  pulmonary  artery,  as 
alfo  at  the  mouth  of  the  aorta,  are  fituated,  in  an 
annular  or  circular  pofition,  three  valves  much 
fmaller  indeed  than  thofe  already  defcribed,  but 
of  a  very  elegant  and  beautiful  figure  and  appear- 
ance, and  furnifhed  with  fiefhy  fibres ;  thefe  have 
been  called  valvule  femilunares  or  Jigmoides. 

§  99- 
Now  it  evidently  appears,  that  by  means  oi 

thefe  different  kinds  of  fmall  valves,  fufficient  pro- 
vifion  is  made  againfl:  the  irregular,  confufed  and 
retrograde  movement  of  the  blood.  They  eafily 
yield,  and  afford  a  paffage  to  the  blood  when  ad- 
vancing regularly  forward  in  the  edabliflied  courfe 
E  3  of 


7©  OF  THE  HEART. 

of  its  circulation.  But  they  prevent  the  regurgir 
tation  of  this  fluid,  by  becoming,  in  confeq.  ence 
of  its  refluent  effort,  fully  expanded  like  the  fwell- 
ing  of  a  well-filled  fail,  and  thus  completely  clofing 
the  orifices  round  which  they  are  arranged. 

§    IOO. 

The  valve  of  Euflachius  which,  in  the  fcetal 
ftate,  is  {Tretched  like  a  curtain  acrofs  the  mouth 
of  the  afcending  cava,  becomes  after  birth  (fooner 
or  later  in  different  fubjedls)  fo  gradually  oblite- 
rated for  the  mod  part,  as  to  be  rendered  wholly 
unfit  for  the  execution  of  its  former  functions; 
neither  indeed  does  the  fyflem  (land  any  longer  in 
need  of  it,  as  a  paflage  is  now  opened  and  prepa- 
red for  the  blood  through  the  lungs,  and  its  re- 
turn from  thofe  vifcera  prevented  by  the  fcmihi- 
nar  valves  already  fpoken  of,  and  as  each  fubfe- 
quent  column  of  blood,  prcfling  from  behind,  mufl 
purfue  the  fame  route  with  that  immediately  pre- 
ceding it.  But  as  it  does  fometimes  notwithfland- 
ing  happen,  that  the  paffage  of  the  blood  from 
the  right  fide  of  the  heart  into  the  lungs  is  by 
fome  means  obftructed,  we  then  learn  from  the 
preternatural  pulfation  obfervable  in  the  fapericr 
cava,  that  the  blood  is  repelled  in  a  retrograde  di- 
rection from  the  right  fmus  into  the  two  adjoining 
great  venous  trunks. 

§    I0Q; 


OF  THE  HEART.  ?l 

§    101. 

It  is  a  point  of  controvcrfy,  whether  or  not  the 
femilunar  valves  fufFer  the  ventricles  to  be  perfect- 
ly and  completely  evacuated,  or  whether  they  do 
not  rather  by  means  of  their  expanfion  intercept 
a  part  of  the  blood  in  its  efcape  from  thofe  cavi- 
ties, and  thus  force  it  to  take  in  fome  meafure  a  re- 
trograde courfe. 

Obfervations  made  on  frogs,  and  even  on  the 
minute  heart  of  the  nafcent  chick,  prove  that  in 
thofe  animals  the  heart  is  indeed  completely  eva- 
cuated ;  but  whether  or  not  the  fame  thing  takes 
place  in  man  himfelf,  when  in  a  found  ftate  of 
health,  is  not  yet  clearly  afcertained  ;  if,  however, 
it  be  admiffible,  in  phyfiological  difcuffions  to  fpe- 
culate  and  draw  conclufions  from  the  ftru£hire  and 
mechanifm  of  thofe  valves  themfelves,  as  they  ap- 
pear on  the  dhTe&ion  of  the  heart,  the  contrary 
opinion  appears  the  mod  probable. 

§  102. 
The  texture  of  the  heart  is  altogether  lingular, 
and  peculiar  to  that  organ.  Ic  is  indeed  fldiiy, 
but  remarkably  clofe  and  compact,  and  widely  dif- 
ferent from  the  common  conflitution  and  appear- 
ance of  mufcles. 


It 


72  OF  THE  HEART. 

It  is  compofcd  of  fmall  bundles  of  fibres,  more 
or  lefs  oblique,  frequently  ramifying  in  a  lingular 
manner,  contorted  and  wound  fpirally  in  diverii- 
lied  and  truly  ftrange  directions ;  thefe  fibres  lie 
over,  and  reft  on,  each  other  in  certain  orders  of 
ftrata,  they  are  intermingled  and  clofely  knit  to- 
gether in  the  feptum  which  feparates  the  two  ven- 
tricles, and  are  faflened  and  firmly  connected  at 
the  bafis  of  thofe  ventricles  by  four  cartalaginous 
rings  or  bands,  which  (according  to  the  accurate 
unravelling  and  developement  of  the  whole  fibrous 
texture  of  the  heart,  lately  executed  by  the  inde- 
fatigable and  illuftrious  Wolff),  appear  to  ferve  as 
a  flay  and  fupport  to  the  Jlefljy  Jlraclure  of  the 
ventricles,  and  alfo  to  feparate  and  difiinguiih  it 
from  the  fibres  of  the  fmufes. 

§  103. 
Thofe  fiefhy  fibres  are  every  where  overfpread 
with  an  infinitude  of  fmall  nervous  ramifications 
of  extreme  foftnefs,  but  they  are  more  particularly 
fupplied  with  fuch  an  immenfe  apparatus  of  blood 
vefftls,  aiifing  from,  and  belonging  to,  the  coro- 
nary arteries  and  veins,  that  Ruyfch  has  declared 
in  his  writings,  that  the  whole  fabric  of  the  heart 
appears  to  be  compofed  folely  of  fanguiferous 
tubes. 

§    i°4- 


OF  THE  HEART.  73 

§    104. 

By  means  of  the  foregoing  Jlruclure  (§  90. 
feq.)  and  texture  (§  101.  feq.)  the  heart  is  fitted 
for  the  performance  of  thofe  perpetual  and  uni- 
formly equable  movements,  which  return  in  fuch 
general  order,  that  the  preliminary  appendices 
and  ventricles  themfelves,  are  alternately  contrac- 
ted and  relaxed,  or  perforin,  in  alternate  times, 
thofe  motions,  called  in  phyfiological  language, 
fyftole  and  diajlole. 

§    105. 

With  fuch  definitude  do  they  preferve  this  har- 
monious order  in  their  routine  of  contraction  and 
dilatation,  that  as  foon  as  the  appendices  contract, 
themfelves,  to  propel  the  blood,  returning  from 
the  lungs  and  vence  cava?,  into  the  ventricles, 
thefe  latter  are  at  the  fame  inftant  relaxed  and 
fitted  to  receive  the  fame  advancing  wave  of 
blood  ;  but  in  the  fubfequent  and  next  moment, 
when  it  is  the  point  of  time  for  the  ventricles, 
now  recently  filled,  to  contract  and  force  the  blood 
into  the  two  arterial  trunks,  the  appendices  are 
again  relaxed,  and  their  mouths  rendered  patulous 
for  the  purpofe  of  drinking  in  a  frefh  tide  of  ve- 
nous blood  as  it  rolls  on  in  its  ufual  courfe. 

§    icO. 


*4  OF  THE  HEART. 

§    1 06. 

This  fyflole  of  the  ventricles,  which  is  fuppoi'ed 
to  confume  about  one  third  part  of  the  whole  time 
of  the  heart's  pulfation,  is  pt  rformed  in  fuch  a 
manner,  that  the  exterior  fides  of  thofe  cavities 
are  approximated  and  cortr  cted  towards  the  in- 
tei-mediate  feptum  which  feparates  the  right  ven- 
tricle from  the  left;  which  contrnclion,  efpecially 
if  we  attend  to  the  conical  h*  ure  of  thofe  cavities, 
appears  fully  fufficient  to  evacuate  them  of  their 
contents. 

But  befides  this  approximation  of  the  lateral 
parts  of  the  heart  towards  each  other,  the  apex 
of  that  organ  is,  during  its  fyflolic  motion,  con- 
tracted towards,  and  brought  nearer  to  its  bafis  ; 
as  has  been  frequently  obfcrved  not  only  in  the 
inferior  animals  both  of  cold*,  and  zuarm  blood, 
but  even  in  man  himfelf,  while  in  a  living  ftatef. 

*  I  have  not  in  the  live-di  flection  of  any  animal  discover- 
ed the  heart  more  evidently  fhortened,  during  its  fyftolic 
motion,  than  in  that  of  coluber  vatr'tx  or  water  ferpent. 
Throughout  the  forelts  in  the  neighbourhood  of  our  city, 
this  fpecies  of  ferpent  may  be  fometimes  found  four  feet  in 
length.  Having  taken  one  of  thefe  animals  and  fufjectcd  it 
in  a  living  Mate  to  the  anatomic  knife,  I  obferved  that  the 
length  of  its  heart  during  the  diajlolie,  exceeded  its  length 
during  thcjjjlo/ic  motion,  at  lead  tire  fpace  of  two  lines. 

f  It  does  not,  however,  appear  that  this  diminution  of 

the  longitude  of  the  heart  during  its  fyftolic  motion  is  an  ab,. 

4  folute 


OF  THE  HEART.  75 

An  argument  feemingly  in  favour  of  a  contrary- 
opinion  has  been  derived  from,  and  founded  in, 
vulgar  experience,  from  which  it  appears  that  the 
apex  of  the  heart  ftrikes,  during  its  fyftolic  mo- 
tion, againft  the  left  mamma  or  bread,  and  feems 
therefore  to  be  rather  elongated  than  contracted 
and  fhorrened  ;  this  apparently  conclufive  argu- 
ment will  however  have  no  weight  with  one  who 
confiders,  that  thofe  fenfible  percuffions  or  flrok.es 
of  the  heart  are  to  be  attributed  as  well  to  the  im- 
petus  of  the  venous  blood  ruining  into  the  appen- 
dices of  that  organ,  as  to  that  of  the  arterial  blood 
forcibly  ejected  from  its  ventricles  ;  by  both  which 
fources  of  propulfion  the  whole  heart  is  carried 
towards  and  impinged  againd  that  region  of  the 
ribs. 

§    '©7- 
The  impetus,  which  is  by  this  fyftolic  contrac- 
tion of  the  heart  imparted  to  the  blood,  is  coiri- 

folute  condition  of  life.  I  am  led  to  the  adoption  of  this 
opinion  from  a  variety  of  obfervations  made  on  the  heart  of 
a  duck,  in  a  grtat  portion  of  which  a  complete  offificatinn 
had  taken  place.  This  heart  was  depolited  in  my  anatomi- 
cal colleftion  by  my  very  liberal  and  worthy  friend  C.  F.  Mi- 
chaelis,  and  is  marked  by  completely  offif  ed  ftrice  running 
from  its  bafe  to  its  apex.  On  its  fides,  however,  it  was  {till 
furnifhed  with  fkfliy  fubftance  fufficient  to  continue  the  late- 
ral motion  of  its  ventricles;  and  thus  preferve  the  circulation 
of  die  blood. 

jmunicated 


-j6  OF  THE  HEART. 

municated  to  the  arterial  fyftem,  receiving  the 
blood,  in  fuch  a  manner,  that  every  fyftole  of  the 
heart  may  be  plainly  perceived  in  fuch  arteries  of 
the  other  parts  of  the  body  as  can  be  fek  by  the 
touch,  (of  which  defcription  are  all  thofe  that  ex- 
ceed  in  their  diameters  the  fixth  part  of  a  line), 
and  liktwiie  in  fuch  other  arteries  as  can  by  any 
means  whatever  have  their  pulfations  rendered 
obvious  to  the  fenfes  :  this  can  be  eafily  effected, 
for  example,  in  the  internal  ear  or  eye,  in  either 
of  which  a  fingular  kind  of  motion  can  be  excited 
and  rendered  fenfible,  which  (as  well  as  the  fame 
kind  of  throbbing  or  pulfatory  motion  fo  percep- 
tible in  the  other  parts  of  the  arterial  fyftem)  is 
called  the  diaftole  of  the  arteries  :  of  this  diaftolic 
motion  we  (hall  have  an  opportunity  to  fpeak  on 
a  future  occafion,  at  which  time  we  will  take  up 
the  inquiry,  whether  or  not  it  is  to  be  attributed 
folely  to  the  action  of  the  arteries  themfelves,  or 
derives  its  exiftence  from  fome  other  fource. 

§  108. 
In  whatever  manner  this  point  may  be  deter- 
mined, one  thing  we  learn  from  experience,  the 
fureft  guide  to  truth,  viz.  that  in  a  healthy  fub- 
jec~t,  what  is  called  the  pulfe  of  the  arteries,  is 
precifely  fynchronous  with,  and  perfectly  corref- 
pondent  to,  the  motions  of  the  heart ;  and  like- 
wife  in  a  morbid  intermiflion   cf  the  pulfe,  the 

heart 


OF  THE  HEART.  77 

heart  and  arteries  (till  harmonize  in  their  action, 
by  eeafing  from,  and  again  commencing,  motion 
at  precifely  the  fame  moments. 

§  109. 
The  frequency  of  the  pulfations  of  the  human 
heart  in  a  healthy  (late,  is  extremely  different  in 
different  fubjects.  This  diverfity  arifes  principally 
from  diverfity  in  point  of  age,  but  partially  alfo 
from  other  conditions  of  the  fyffem,  which  at  any 
and  every  period  of  life  conftitute  the  health  pro- 
per to  each  individual  ;  fo  that  it  is  not  pofliblc 
to  afcertain  and  eltablifh,  on  this  fubjecl,  any  cer- 
tain and  definite  rule.  It  may  neverthelefs  be  pro- 
per to  mention  the  general  refult  of  my  obferva- 
tions  (made  in  our  own  climate)  on  the  frequency 
of  the  pulfe  in  the  different  periods  of  human  life. 

In  the  firft  days  after  birth  I  have  generally 
found  the  pulf  itions  of  the  heart  of  the  tender  in- 
fant, while  found  afleep,  amount  to  about  140  in 
the  fpace  of  a  minute. 

At  the  expiration  of  the  firfl  year,  they  amount 
to  124  iu  a  minute. 

At  the  end  of  the  fecond  year  to  about  1 10. 

At  the  end  of  the  third  year  to  about  96,  &c. 

At 


7*  OF  THE  HEART. 

At  that  period  in  which  the  firft  fet  of  teeth, 
ufually  culled  the  milk -teeth,  drop  out,  the  pulfa- 
tions  of  the  heart  amount  to  86  in  a  minute. 

At  the  age  of  puberty  to  about  80. 

In  the  prime  of  life,  or  at  the  period  of  man- 
hood, to  about  j$. 

And  to  about  60  at  the  fixtieth  year  of  human 
life. 

In  fubjedls  ftill  farther  advanced  in  years,  I  have 
fcarcely  found  two  in  whom  the  number  of  pulfa- 
tions  were  the  fame,  at  the  fame  period  of  old 
age. 

§    no. 
All  other  circumftances  being  alike,   the  pulfa- 
tions  of  the  heart  are  more  frequent  in  females 
rhan  in  males. 

If  proper  and  neceffary  allowance  be  made  for 
the  habit  of  body,  they  are  lefs  frequent  in  men 
uncommonly  tall,  than  in  fuch  as  are  rather  low. 
This  circumftance  I  have  afcertained  to  be  a  truth 
by  comparative  obfcrvations  made  on  the  pulfes 
of  dwarfs,  and  giants  or  men  remarkably  large. 

§   n  i« 


OF  THE  KEARTv  79 

§    III. 

On  the  fubjeft  of  thofe  varieties  in  the  pulfe* 
occafioned  by  extraneous  circumjiances,  vulgarly 
called  non-naturah,  it  is  neceffary  to  obferve,  that 
a  Cold  climate  produces  a  flow  pulfe  ;  thus,  for 
inftance,  the  heart  of  a  Greenlander  when  in 
perfect  health,  does  not  pulfate  oftner  than  from 
thirty  to  forty  times  in  a  minute. 

But  it  is  an  obfervation  as  common  as  it  is 
true,  that  the  pulfe  becomes  more  frequent  after 
the  taking  in  of  aliment,  and  after  an  emiffion  of 
femen*  The  fame  effect  is  alfo  produced  on  the 
pulfe  by  a  want  of  deep,  by  bodily  exercife,  or 
by  paffions  of  the  mind. 

The  foregoing  obfervations  relate  to  the  na- 
tural or  healthy  pulfe,  in  the  confideration  of 
which  it  feems  more  confident,  and  agreeable  to 
nature,  to  direft  our  views  to  the  heart,  as  its  ex* 
clufive  fource,  than  to  the  arteries,  on  which 
phyfiologifls  have  ufually  fixed  their  attention 
when  engaged  in  the  inveiligation  of  this  fubjecT:. 

In  this  inceffant  routine,  the  heart  continues  its 
pulfations,  down  to  the  extreme  glimmerings  of 
life's  perifhable  flame  ;  and  even  then,  all  its  parts 
tlo  not  ceafe  from  a&ion  at  the  fame  moment, 

but 


tto  i)F  THE  HEART. 

but  it  is  the  prerogative  of  the  right  ventricle 
with  its  appendices,  the  right  auricle  and  finous, 
furvive  the  left  ventricle,  and  its  appendices. 

This  may  be  fufficiently  illuftrated  in  the  fol- 
lowing manner  :  After  the  laft  act  of  expiration, 
the  lungs  now  in  a  collapfed  ftate,  can  no  longer 
admit  the  blood  to  flow  through  them  in  its  cuf- 
tomary  channel,  while  at  the  fame  time  that  wave 
of  blood  which  they  have  jult  returned  to  the  left 
fide  of  the  heart,  is  from  thence  forccably  expel- 
led through  the  aorta,  and  thus  urges  forward  by 
a  ids  a  tergo  the  advancing  column  of  venous 
blood  :  from  this  combination  and  concurrence 
of  circumftances,  the  blood  returning  with  preci- 
pitation and  impetuofity,  ruflies  violently  into  the 
appendices  and  ventricle  on  the  right  fide  of  the 
heart,  in  confequence  of  which  the  parietes  of 
thofe  cavities  are  thrown  into  convuliive  efforts, 
and  thus  continue  to  be  agitated,  for  fome  time, 
after  the  left  fide  of  that  organ  is  completely  de- 
prived of  all  vital  motion. 

§    1*3- 

From  a  knowledge  of  this  fad,  viz.  that 
during  the  laft  vital  efforts  of  declining  nature, 
the  blood  is  propelled  into  the  cavities  on  the 
right  fide  of  the  heart,  we  deduce,  with  the  ut- 
moft  eafe,  the  caufe  of  that  ftate  of  depletion  in 
i  which 


OF  THE  HEART.  Si 

which  the  larger  arteries  are  found  after  death. 
To  the  fame  caufe  aifo  Weifs,  and  after  him  the 
illuftrious  Sabatier,  were  defirous  of  attributing 
the  fuperior  fize  of  the  cavities  on  the  right,  to 
that  of  thofe  on  the  left,  fide  of  the  heart,  efpe- 
cially  in  the  corpfe  of  an  adult  fubjecT:. 

§    H4- 

The  whole  of  this  motion  of  the  heart,  which 

has  been  the  fubject  of  the  preceding  obferva- 
tions,  is  to  a  very  confiderable  degree  limited  and 
dire&ed  by  the  pericardium,  in  which  the  heart 
loofely  hangs,  and  by  which  it  is  completely  en- 
clofed  as  in  the  walls  of  a  prifon. 

The  pericardium  is  a  membranous  fac,  confid- 
erably  capacious,  and  accommodated  to  the  figure 
of  the  heart  which  it  enclofes.  It  takes  its  oricrin 
from  the  membranes  conftituting  the  mediaftinum, 
and  although,  from  its  finenefs,  it  may  appear  fome- 
what  tender,  yet  we  learn  from  the  experiments 
of  Wintringham,  that  it  is  fo  very  tenacious  and 
firm,  as  far  to  exceed  in  (Irength  all  other  mem- 
branes of  a  fimilar  nature  in  the  human  body. 

That  the  pericardium   is   a   part   of  the   firft 

importance    in    the    animal    economy,    we   fafely 

infer  from  this  fingle  circumftance,  namely,  that 

throughout  all  claffes   of  animals  pofTefling  red 

voi..  i.  F  blood, 


82  OF  THE  HEART. 

blood,  it  is  found  as  conftantly  and  uniformly  ex- 
iting as  the  heart  itfelf ;  and  records  do  not  fur- 
nilh  more  than  one  or  two  examples  of  the  human 
heart  having  been  found  completely  deftitute  of  a 
pericardium.  Thefe  fingular  examples  of  fuch  an 
unnatural  (late  of  the  heart  are  recorded  in  the 
writings  of  Dinkier. 

§    115. 
The  internal  furface  of  the  pericardium  is  kept 
conftantly  humid  by  a  dew-like  ferous    efTufion, 
which  appears  to  exhale  from  the  fmall  arteries 
of  the  heart  itfelf. 

In  like  manner  a  fluid,  of  a  fimilar  nature,  ap- 
pears to  tranfude  into  the  very  cavities  of  the 
heart,  and  to  moiften  and  lubricate  their  furround- 
ing  parities  or  walls. 

In  either  cafe  the  efTufion  during  the  healthy 
flate  of  the  part  is  of  a  ferous  nature,  and  not  ac- 
companied by  any  real  lymph,  unlefs  the  heart  be 
labouring  under  inflammation  ;  but  when  this  or- 
gan becomes  the  feat  of  an  inflammatory  affection, 
then  genuine  lymph  tranfudes,  giving  rife,  on  the 
external  fuperficies  of  the  heart,  to  fine  filaments 
of  a  hair-like  appearance,  together  with  thofe 
preternatural  portions  of  cellular  membrane, 
which  in  fuch  cafes   connect   the   heart  to   the 

pericardium. 


POWERS,  &c.  83 

pericardium,  but  on  the  interior  furfaces  of  the 
cavities  themfelves  producing  excrefcences  of  a 
truly  polypous  nature.     (§  19.) 


SECT.     X. 


OF  THE  POWERS  BY  WHICH  THE  BLOOD  IS 
KEPT  IN  MOTION. 

_LlAVING  thus  completed  the  confid- 
cration  of  the  organs  in  which  the  blood  is  con- 
tained, we  now  pafs  on  to  take  a  view  of  the 
powers,  by  which  thofe  organs  are  qualified  and 
fully  prepared  to  keep  that  vital  fluid  in  motion. 

Let  us,  in  the  firft  place,  take  an  attentive  and 
accurate  furvey  of  thofe  powers  which  refide  in 
the  heart  itfelf,  and  which  ought,  without  doubt, 
to  be  confidered  as  by  far  the  mod  active  and  ef- 
fential  in  the  great  buiinefs  of  circulation  :  we 
will  then  proceed  to  confider  what  may  be  called 
the  fecondary  and  affiftant  powers,  which  we  will 
alfo  find  of  high  importance  in  the  animal  econo- 
my, from  the  concurrent  and  effective  aid  which 
they  afford  to  the  action  of  the  heart. 

F  2  5    117. 


*4  POWERS  WHICH  KEEP 

§  117- 
It  will  at  firft  view  appear  obvious  to  even  the 
moil  fuperficial  obferver,  that  it  is  a  matter  of 
Herculean  difficulty  indeed,  either  to  afcertain  by 
accurate  calculation  the  force  of  action  exerted 
by  the  heart,  or  to  determine  with  precifion  the 
quantity  of  blood  thrown  into  the  aorta  by  that 
organ  at  each  pulfation  ;  neither  will  the  fpecula- 
tive  phyfiologifl  find  himfelf  belet  with  difficulties 
of  lefs  moment,  when  he  attempts  to  afcertain  and 
eftabliih  with  definitude,  either  the  diftance  to 
which  each  projected  wave  of  blood  is  carried  by 
the  impetus  it  receives  from  the  heart  alone,  or 
yet  the  celerity  with  which  fuch  wave  rolls  for- 
ward ;  but  he  will  be  furrounded  with  difficulties, 
ftill  encreafing  at  each  advancing  ftep,  in  his  at- 
tempts to  render  a  jufl  ftatement  and  accurate  ac- 
count of  all  fuch  obftacles  as  oppofe,  and  thus 
greatly  diminiih  the  effects  of  the  force  exerted 
by  the  heart,  in  its  action  on  the  circulating  maf> 
of  fluids. 

§  118. 

A  certain  eflimation  may  neverthelefs  be  formed 
of  the  power  of  the  heart,  by  collecting  and  com- 
paring the  mod  probable  conjectures  which  have 
appeared  on  the  above  points  of  phyfiological  fpe- 
culation.  Thus  for  inftance,  if  we  fuppofe  the 
whole  mafs  of  blood  to  amount  at  a  mean  rate  to 

33 


THE  BLOOD  IN  MOTION.  8$ 

^  pounds,  i.  e.  396  ounces  (§  23),  and  eftimate 
the  number  of  pulfations  at  75  in  a  minute,  /.  e. 
4500  every  hour  (§    109)  ;    and   further,   if  we 
adopt  the  opinion  that  at  each  fyftole  the  left  ven- 
tricle ejefts  two  ounces  of  blood,  it  will  then  fol- 
low,  that   during  the  courfe  of  every  hour  the 
weight  of  the  whole  volume  of  blood  makes  11% 
complete  tranfitions  through  the  heart.     We  may 
alfo    form  a  tolerable  conception  and   eftimation 
of  the  impetus  with  which  the  circulating  blood 
is  propelled  from  the  left  ventricle  of  the  heart, 
by  obferving  with  what  aftonifhing  violence,  and 
to  what  a  confiderable  height,  the  blood  fpouts 
from  one  of  the  larger  arteries  when  wounded  in 
the  neighbourhood   of  the  heart.     Thus,   from 
the  wounded  carotid  of  an  adnlt  fubjedl,  I  have 
feen  the  blood,   during  a  few  of  the  firft  contrac- 
tions of  the  heart  after  the  accident,  mount  in 
jets  to  the  height  of  at  lead:  five  feet. 

§    JI9« 
But  when  we  inftitute  an  enquiry  for  the  dif- 

covery   of  thofe  unfailing   fountains    or   fprings, 

which  fupply  the  heart  with  a  force  fo  powerful, 

and  at  the  fame  time  fo  uninterrupted  and  lafting, 

that  which  firft  attracts  our  attention,  as  being 

foremoft  both  in  point  of  time  and  importance  is 

its  irritability ',  (§  44).     This  vital  energy,  as  has 

teen  already  evinced  (§  90),  is  much  longer  pof- 

F  3  fefled 


86  POWERS  WHICH  KEEP 

fefTed  by  the  heart,  than  by  any  other  mufcular 
part  in  the  whole  human  body. 

That  the  parietes,  or  walls  themfeves  of  the 
cavities,  are  irritated  and  excited  to  contract  by 
reiterated  impreffions  from  the  circulating  waves- 
of  blood,  is  manifeft  from  a  well  known  experiment 
of  the  illuftrious  Haller.  From  this  celebrated 
experiment,  of  that  indefatigable  phyfiologift  and 
acute  philofopher,  it  appears,  that  he  could  at 
pleafure  grant,  either  to  the  right  or  left  fide  of 
the  heart,  the  prerogative  of  a  more  protracted 
vital  motion,  (/".  c.  of  longer  life)  accordingly  as 
he  firil  deprived  the  one  fide  or  the  other  of  its 
peculiar  flimulus,  the  blood*. 

§    120. 

When  the  proportional  quantity  of  the  blood 
is  well  adjufled  to  the  fize  of  the  containing  veiTels, 
and  its  quality  uncontaminated  by  any  morbid 
change,  its  action  on  the  heart,  and  the  re-action 
of  that  organ  again  on  the  blood,  proceed  with 
fuch  an  equable,  regular  and  happy  facility,  that, 
when  in  a  (late  of  reft,  we  are  fcarcely  fenfible  of 
the  circulation  of  this  vital  fluid,  which  is  the  kind 
and  condant  difpenfer  of  life  and  vigour  to  every 
part  of  our  bodies. 

*  See  Haller  "  De  motu  cordis  a  ftimulo  r.ato,"  in 
Cornmentur.  Soc.  Sc'.ent.  Goettingeas,  torn.  i. 

Bat 


THE  BLOOD  IN  MOTION.  87 

But  if  the  circulating  volume  of  blood  be  either 
too  abundant,  or  preternaturally  fcanty,  but  efpe- 
cially  if  this  vital  fluid  be  contaminated  by  the 
admixture  of  any  foreign  fubftance,  as  noxious 
miafmata,  air  in  an  elaftic  flate,  or  poifons  in- 
jected into  the  veins,  &c.  the  heart,  either  roufed 
immediately  into  excefiive  action,  or  deprefied  to 
the  oppofite  extreme  of  proftration  and  debility, 
continues  no  longer  fit  for  the  falutary  difcharge 
of  its  important  function,  but  falls  into  motions 
convu'five,  irregular,  and  very  widely  different 
from  the  equable  tenor  of  its  healthy  action.  Fo- 
reign fubftances  of  the  fame  kind,  as  air  blown 
into  the  veins,  &c.  are  alfo  fometimes  able  to 
roufe  again,  and  excite  to  motion,  the  heart  of  an 
animal  recently  dead. 

§    121. 

It  has  been  a  point  of  controverfy,  even  in  very 
modern  times,  whether  this  extreme  irritability  of 
the  heart  be  eflfentially  inherent  in  its  own  fub- 
ltance,  or  if  it  be  not  rather  adventitious,  and  de- 
rived, as  fome  celebrated  characters  would  induce 
the  world  to  believe,  from  rhe  myfterious  influence 
of  the  nerves  ?  We  will  hereafter  have  a  fit  oppor- 
tunity of  declaring  our  fentiments  refpedting  the 
whole  of  this  controverfy,  when  we  come  to  con- 
fider  the  doctrine  of  mufcular  irritability,  under 
which  head,  this  fubject  of  inquiry  mod  naturally 
F  4  falls. 


SS  POWERS  WHICH  KEEP 

falls.  On  the  prefent  occafion  it  may  fufficc  to 
obferve,  that  I  am  daily  more  and  more  convinced, 
that  irritability  is  a  fpecics  of  vital  energy  altoge- 
ther peculiar  in  its  nature,  belonging  exclusively 
to  mufcular  fibres,  and  completely  diftincl:  from 
the  vis  nervea  (§  34,  45.)  But,  on  the  other 
hand,  it  is  no  lefs  evident  and  incontrovertible, 
that  the  nerves  do  alfo  polfefs  a  very  powerful  in- 
fluence and  command  over  the  action  of  the  heart : 
this  we  learn,  as  well  from  the  peculiar  habit  and 
appearance  of  the  cardiac  nerves,  from  their  foft- 
nefs,  their  defect  of  covering,  and  their  fingular 
difpofition  and  arrangement,  as  from  the  aftoniih- 
ing  confent  of  the  heart  with  by  far  the  greater 
number  of  the  functions  of  the  human  body,  even 
with  thofe  of  the  mod  oppofite  nature.  In  tefli- 
mony  of  the  reality  of  this  confent,  it  may  be 
fufficient  barely  to  mention,  the  fudden  and  tran- 
fient  fympathy  which,  even  in  a  healthy  fubjec"t, 
exifts  between  all  the  pafhons  of  the  mind  and 
the  heart,  together  with  that,  which,  in  a  great 
many  fpecies  of  difeafe,  manifests  itfelf  between 
this  organ  and  the  prima  via. 

§    122. 

But,  befides  ihofe  vital  energies  of  the  heart, 

it  poirefTcs  alfo  another  power,  arifmg  out  of  its 

mechanical  ftru&ure,  which  appears  to  contribute 

not  a  little  towards  carrying  on  the  circulation  of 

the 


THE  BLOOD  IN  MOTION.  89 

the  blood.  The  cavities  of  this  organ  being 
clofely  contracted,  in  the  time  of  its  f) dole,  and 
the  blood  by  this  means  completely  expelled,  a 
vacuum  is  thus  produced,  into  which,  on  the  prin- 
ciples of  the  well  known  law  of  derivation,  the 
neighbouring  blood  muft  of  neceffity  flow  ;  for,  as 
the  valves  prevent  the  regurgitation  of  the  wave 
juft  ejected,  it  follows  of  courfe,  that  the  cavities 
of  the  heart  muft  then  drink  in,  and  fwallow  down, 
with  rapidity,  the  blood  advancing  in  the  trunks 
of  the  veins. 

§  i23- 
We  proceed  now  to  enquire,  whether  or  not, 
any  of  the  other  organs  through  which  the  blood 
pafles,  befides  the  heart  itfelf,  are  furnifhed  with 
powers  contributary  to  the  continuance  of  the 
circulation  of  that  fluid.  Judging  from  firft  prin- 
ciples, or  a  priori,  as  it  is  termed,  we  are  led  to 
fufpedt  that  fuch  powers  do  exift  ;  for  it  appears 
hardly  probable,  that  the  wifdom  of  nature  has 
entrufied  fo  important  a  function,  on  which  the 
life  of  fanguiferous  animals  immediately  depends, 
to  one  organ  only,  the  faults  and  defects  of  which 
might,  in  fuch  cafe,  with  too  much  facility,  be 
attended  with  fatal  confequences.  But,  reafoning 
a  po/leriori,  as  they  term  it,  i.  e.  from  actual  cb- 
fervations,  made  on  the  animal  economy,  we  are 
furnifhed  with  numerous  facts  fufficiem  to  eitablifh, 

beyond 


po  POWERS  WHICH  KEEP 

beyond  a  doubt,  the  exiftence  of  fuch  poweis, 
which  we  may  therefore  term  fecondary  powers, 
and  which  are  able,  not  only  to  aid  the  action  of 
the  heart,  but,  in  fome  cafes,  to  compenfate  for 
almoft  the  complete  abfence  of  the  influence  of 
that  important  organ.  A  finking  inftance  of  this 
nature,  is  the  continued  motion  of  the  blood,  in 
certain  parts  of  the  body,  on  which  the  power  of 
the  heart  can  have  but  very  little  effect,  if  indeed 
it  can  extend  to  them  at  all :  this  phenomenon  is 
obfervable,  as  well  in  the  venous  fyflem  of  the 
liver,  ns  in  the  placenta  of  the  uterus ;  not  to 
mention  numerous  instances  of  feetufes  having 
been  born,  without  the  fmalleft  vefiige  of  a  heart. 

§  i-*4- 

Of  thefe  fecondary  poivcrs,  the  mft  to  be  men- 
tioned is,  the  j "unci "ions  of  the  Arteries,  the  influ- 
ence of  which,  in  promoting  and  continuing  the 
circulation  of  the  blood,  appears  to  be,  indeed, 
very  confiderable ;  although  the  true  principles 
and  mode  of  their  action,  on  this  fluid,  have  not 
yet  been  fully  developed  and  eflablifhed. 

Speaking  in  general  terms,  there  exifls  a  very 
confiderable  refemblance  between  the  arteries  and 
the  heart  itfclf:  that  the  arteries,  for  example, 
have  a  mufcular  coat,  is  a  facl  of  the  utmoft  pub- 
hn:y(§;2.) 

That 


THE  BLOOD  IN  MOTION.  91 

That  they  alfo  poflefs  irritability,  has  been  very 
generally  known,  fince  the  famous  experiments  of 
the  illuftrious  Verfchuir. 

And,  further,  as  the  afpect  or  difpofition  of  the 
cardiac  nerves  on  the  heart  itfclf  is  truly  fingular, 
thus  alfo  the  larger  branches  of  the  arteries  are, 
here  and  there,  furrounded  with  aflonifhing  reti- 
cular intertextures  of  foft  nerves. 

§  125. 
Finally,  It  is  well  known  to  every  one  that  the 
arteries  pulfate,  and  that  indeed  with  fuch  vehe- 
mence and  force,  that  if  we  fuffer  one  of  our  legs 
to  lie  over  the  other  knee,  the  pulfations  of  the 
popliteal  artery  are  fufficient  to  elevate  in  a  fub- 
fultory  manner,  the  fuperincumbent  leg  not  only 
alone,  but  even  with  a  very  confiderable  weight 
appended  to  it.  Indeed  for  a  long  time  pall:,  both 
a  fyftolic  contraction  and  diaftolic  relaxation  have 
been  attributed  to  the  arteries,  which  motions 
have  been  faid  to  correfpond  and  harmonize  with 
the  alternate  contractions  and  dilatations  of  the 
ventircles  of  the  heart. 

Though  the  truth  of  this  laft  propofition  is 
generally  believed  to  be  eftablifhed  and  confirmed 
by  the  fimple  teftimony  of  the  fenfes  themfelves, 
the  fubjeft  is  neverthelefs  flill  embarralTed  with 

various 


92  POWERS  WHICH  KEEP 

various  doubts  and  difficulties :  thefe  difficulties 
immediately  rife  to  view,  when  it  is  aiked, 
whether  this  vibrating  or  pulfatory  motion, 
which  is  felt  on  examination  by  the  ringer,  is  to 
be  attributed  to  the  inherent  energy  of  the  ar- 
teries, or  to  the  impulfe  of  the  heafrt  ;  and 
whether  the  whole  motion  of  the  arteries  does 
not  depend  folely  on  the  impetus  with  which  the 
blood  is  projected  into  the  aorta,  and  thus  im- 
pinges againft  the  fides  of  that  tube,  and  its  rami- 
fications ? 

DifTe&ions  of  living  animals  have  not  been  fuf- 
ficicnt  to  decide  this  controverfy.  For  it  fome- 
times  happens  that  during  the  live-d'nTections  of 
warm  blooded  animals  you  may  difcover  the  lar- 
ger arteries  pulfating,  while  at  other  times  again 
they  appear  in  a  Mate  of  complete  reft.  In  man 
himfelf,  while  in  the  enjoyment  of  vitality,  I  had 
once  an  occafional  opportunity  of  obferving  the 
neighbouring  trunks  of  the  aorta  and  pulmonary 
artery,  to  be  perfectly  deftitute  of  all  motion  ; 
but  it  fhould  not  be  forgotten,  that  this  phenome- 
non appeared  in  a  cafe  of  monftrous  or  preterna- 
tural formation  of  the  parts.  There  are  alfo  ar- 
teries which  we  fometimes  feel  in  a  ftate  of  violent 
pulfation,  and  which  we  neverthelefs  know,  from 
anatomy,  are,  in  confequence  of  their  fituation, 
almoft  immoveable;   of  this  we  have  an  example 

in 


THE  BLOOD  IN  MOTION.  93 

in  the  cerebral  carotid,  where  it  pafles  through 
the  canal  of  the  os  pctrofum. 

§    126. 
"When  all  circumftances  relative  to  this  fubj eel 
are  impartially  weighed  and  difpaflionately  consi- 
dered, this  appears  to  be  the  refult,  viz.  that  the 
diajlole  or  the  larger  arteries  takes  place  in  confe- 
quence  of  their  peculiar  nature,  and  is  to  be  attri- 
buted to  the  impetus   of  the  blood  milling  for- 
cibly into  them,  and  expanding  their  coats  or  tu- 
nics, which,  by  means  of  their  elafticity,    imme- 
diately return  again   to  their  natural  dimenfions. 
To  the   fame   impulfc  alfo   mould  be  attributed 
that  lateral    or    curving    motion    of  their   axes, 
which  may  frequently  be  obferved  in  the  larger 
arteries  when  they  run  in  a  ferpentine  direction, 
and  lie  einbedded  in  foft  cellular  membrane. 

But  in  a  found  (late  of  the  fyftem,  we  contend 
that  the  arteries  fcarcely  exhibit  any  unequivocal 
proofs  of  a  true  fyftole^  i.  e.  they  do  not  by  a  ge- 
nuine contra&ion  recede  from  their  natural^  to 
fmaller  dimenfions,  as  long  as  the  heart  is  adequate 
to  the  due  performance  of  its  momentous  func- 
tion ;  but  although  it  be  certain,  that  the  arteries 
do  not  always,  yet  we  acknowledge  that  they  do 
fometimes,  exhibit  and  exercife  a  power  of  real 
contraction  :  thus  for  mftance,  when  the  heart  is 

deficient 


94  POWERS  WHICH  KEEP 

deficient  in  its  action  in  confequence  of  labouring 
under  either  a  morbid  oillfication,  or  fome  other 
fpecies  of  difeafe,  it  is  probable  that  then  the 
duties  of  this  important  organ  devolve  on,  and 
are  difcharged  by,  the  arteries,  and  that  the 
blood  is  thus  kept  in  motion  by  the  vital  energy 
of  thofe  animated  tubes. 

§  *27- 

As  it  has  been  the  decided  opinion  of  feveral 
celebrated  phyfiologifts,  efpecially  the  famous 
Whytt,  that  the  powers  of  the  heart  cannot  pof- 
fibly  extend  their  influence  to  blood-veflfels  of  the 
fmallefl:  order,  as,  for  example,  to  the  extreme 
terminations  of  the  arteries,  and  to  the  incipient 
radicles  of  the  veins ;  they  have  therefore  attri- 
buted the  motion  of  the  blood,  in  that  part  of  the 
fyftem,  to  a  cerrain  ofcillatory  action  of  thofe  mi- 
nute veffels  themfelves,  by  the  help  of  which  their 
contents  are  propelled  forward  :  and  this  fame  vi- 
bratory motion  they  have  alio  applied,  with  a 
great  deal  of  ingenuity,  to  explain  and  demon- 
ftrate  the  nature  of  inflammation,  &c. 

There  are  indeed  a  variety  of  phenomena,  as 
well  pbyfwlogical,  which  fhall  be  mentioned  when 
on  the  fubject  of  animal  heat,  as  pathological,  par- 
ticularly obfervable  in  fpafmodic  affections,  ac- 
companied with  fever,   which  feena  to  favour  the 

exiftence 


THE  BLOOD  IN  MOTION.  95 

exiflence  of  fuch  a  power  of  ofcillatory  motion, 
although  no  fuch  motion  has  ever  been  actually 
obferved,  even  with  the  affiftance  of  glafles,  in 
the  diffeclions  of  living  animals. 


•     §    12S. 

It  yet  remains  to  enquire  alfo  after  thofe  afllft- 
ant  powers,  by  which  the  other  parts  of  the  veins, 
befides  their  radicles  or  incipient  roots,  are  fitted 
to  complete  finally  the  return  cf  the  blood  to  the 
heart.  It  appears,  indeed,  at  the  firft  view  of  the 
fubject,  that  the  veins  pofTefs  and  exert  a  much 
imaller  portion  of  the  active  vital  energies  than 
the  other  parts  of  the  fanguiferous  fyftera, becaufe 
the  return  of  the  vital  fluid,  contained  in  thofe 
veilels,  towards  the  heart,  feems  to  be  owing  to 
the  impetus  of  the  arterial  blood  urging  it  on  b\ 
a  vis  a  tcrgo,  as  well  as  to  the  valvular  dructure 
of  the  veins  themfelves,  which  effectually  prevents 
the  blood  from  regurgitating:.  That  thefe  minute 
valves  are  of  the  utmoft  importance  in  promoting 
and  continuing  the  regular  and  free  circulation  cf 
the  blood,  is  fatisfa&orily  demonftratcd  by  the  fre- 
quent congeftioas  and  infarctions,  which  happen  ia 
thofe  veins  that  originate  in  the  inferior  parts  of 
the  abdominal  cavity,  and  which  are  entirely  de- 
ftjtute  of  fuch  valves. 


But 


96  POWERS  WHICH  KEEP 

But  there  arc  neverthelefs  a  variety  of  argu- 
ments which  render  it  probable,  that  the  trunks 
of  the  veins  do  poflefs,  and  actually  exert,  certain 
degrees  of  the  vital  energies ;  as  is  well  exempli- 
fied in  the  veins  of  the  liyer,  and  of  the  uterine 
placenta  (§123.),  &c. 

It  is  alfo  well  known  to  every  one,  that  the  ex- 
periments firft  inftkuted  by  the  illuftrious  Ver- 
fchuir,  are  highly  in  favour  of  the  exiftence  of  a 
vital  energy  in  the  veins. 

And,  that  the  two  leading  and  extreme  venous 
trunks  have  a  ftratum  of  a  true  mufcular  nature, 
we  have  briefly  hinted  on  a  former  occafion 
(§  84). 

§    129. 

Thefe  are  indeed  the  leading  powers  which  are 
aftive  in  promoting  the  circulation  of  the  blood, 
and  which  derive  their  origin  from  the  very 
ftru&ure  of  the  veflels  in  which  this  fluid  is  con- 
tained. I  fay  nothing  of  the  manner  or  degree  in 
which  the  motion  of  this  vital  liquid  is  influenced 
by  weight,  attradion,  or  fuch  other  properties  as 
are  poflefled  by  all  bodies  in  common. 

I  alfo  pafs  over  in  filence  the  more  remote  and 
inconfiderable  aids,  which,  in  a  human  fubject  after 

birth 


OF  RESPIRATION.  97 

birth,  are  afforded  to  the  circulation  of  the  blood, 
by  the  exercife  of  the  other  functionsof  the  fyftem, 
fuch  as  refpiration,  mufcular  motion,  £cc. 


SECT.    XI. 
OF  RESPIRATION,  AND  IT9  PRIMARY  USE. 

§     13°- 

X  HE  lungs,  which  are  very  intimately 
connected  with  the  heart,  as  well  from  the  vicinity 
of  their  fituation,  a*  from  their  uniform  intercourfo 
in  the  performance  of  their  important  function, 
are  two  vifcera,  large  in  the  human  fubject  after 
birth,  but  of  fuch  fpecific  lightnefs,  as  to  float  on 
the  furface  of  water.  They  confifl  of  a  paren- 
chymatous fubftance,  of  a  fpungy  texture,  and 
even  exhibiting  fomewhat  the  appearance  of  foam, 
yet  flill  confiderably  tenacious  and  flrong. 

§   I3l- 
The  lungs  fill  up  the  two  cavities  of  the  thorax, 

and  thus  lie  in  perfect  contact:  with  the  facs  of  the 
pleura,  to  which,  as  well  as  to  the  other  parts 
contained  in  the  thorax,  they  apply  and  accom- 
modate themfelves  with  the  utmolt  defmitude  and 
exact  nefs. 

vol.  1.  G  §    152. 


98'  OF  RESPIRATION'. 

§    '  32. 

Thefe  vi fee r.i  are  appended  to  an  air  tube  com- 
monly called  the  afpera  arteriay  which,  (befides 
an  internal  membrane,  lined  with  mucus,  under 
which  is  expanded  a  nervous  intertexture  of  ex- 
treme fenfibility),  confifls  alfo  of  a  mufcular  coat, 
which  furronnds  the  nervous  expanfion,  and  on 
the  pofterior  fide  is  eafily  diftinguifhed  at  the  ter- 
minations of  certain  cartilaginous  arches,  which 
aflift  in  the  formation  of  the  tube,  but  are  not  uni- 
forra  in  their  number. 

§    133- 

After  the  afpera  artcria  has  entered  the  thorax 
it  firft  forms,  by  bifurcation,  the  two  trunks  of 
the  bronchia,  which  as  they  (hoot  (till  deeper  and 
deeper  into  the  lobes  and  lobules  of  the  lungs,  pafs 
again,  by  reiterated  divifions  and  fubdivifions,  into 
branches  and  ramifications,  uniformly  decreafmg 
in  fize.  During  thefe  progreflive  and  multiplex 
divifions  into  inferior  orders,  both  the  fmall  carti- 
laginous rings,  and  their  mufcular  coat  gradually 
difappear,  till  the  evanefcent  extremities  of  the 
tubes  finally  terminate  in  thofe  minute  cells, 
which  conftitute  by  far  the  greater  and  more  im- 
portant part  of  the  fubft ance  of  the  lungs,  as  their 
office  is  to  receive,  and  again  difcharge  the  vivify- 
ing aerial  element,  in  the  procefs  of  refpiration. 

§    l34- 


OF  RESPIRATION.  pp 

Thofe  fmall  air  cells  do  not  appear  to  poiTcfs 
uniformly,  either  the  fame  figure  or  dimenjions. 
With  refpect.  to  the  former  of  thefe,  (viz.  their 
figure),  it  is  in  general  that  of  a  polyhedron.  The 
latter,  (/'.  e.  their  dimenfions),  as  far  as  their  fqper- 
fieial  extent  is  embraced  in  the  confideration,  can- 
not without  the  utmofi  difficulty,  be  afcertained  ; 
but,  if  we  confider  only  their  aggregate  capacity, 
this,  in  the  lungs  of  an  adult  fubjecl:,  whofe  infpi- 
rations  are  full  and  flrong,  is  fufficient  to  admir 
and  contain  about  60  cubic  inches  of  air.  We  do 
not  here  fpeak  of  the  immenfe  fize,  to  which  the 
lungs  may  be  expanded  by  inflation,  after  the  tho- 
rax is  opened,  but  only  of  the  quantity  and  volume 
of  air  which  they  do  actually  admit  in  the  living 
fubjecl,  when  the  procefs  of  refpiration  is  per- 
formed with  eafe  and  vigour. 

§  l35- 
Thefe  vcftcles  or  cells,  deftined  for  the  reception 
of  air,  are  every  where  furrounded  and  bound 
together  by  that  common,  but  extremely  tender, 
cellular  membrane,  which,  as  we  have  already 
learned,  conftitutes  a  general  vinculum  or  bond  of 
union  to  the  whole  body.  But  it  is  necelTary  to 
diitinguifh  clearly  and  accurately  between  the  two 
kinds  of  cells  which  exiil  in  the  pulmonic  fyiterr.. 
I  have  feen  the  air  cells  fo  feparatc  and  diflin&, 
G  2  ia 


106  OF  RESPIRATION. 

in  the  lungs  of  a  healthy  human  fubje£t,  that  a  per- 
fon's  breath,  gently  and  cautioufly  blown  through 
a  very  minute  and  tender  ramification  of  the  bron- 
chia, would  elevate  only  a  fingle  circumfcribed 
ciufter  or  veflels  or  cells,  and  would  neither  pafs 
into  the  neighbouring  cells  of  the  fame  kind,  nor 
yet  into  the  common  cellular  membrane,  which  is 
every  where  interpofed  between  thofe  ceils  in- 
tended for  the  reception  of  air.  But,  if  the  breath 
be  urged  with  confiderable  force,  the  air  cells 
will  be  lacerated,  and  fuch  a  communication  form- 
ed with  the  furrounding  cellular  membrane,  as  to 
give  free  pafTage  to  the  fubtle  elaftic  fluid,  and 
thus  the  whole  and  every  part,  of  the  pulmonary 
lobe,  will  appear  to  be  inflated. 

§    J36- 
This   exceedingly  tender  cellular  membrane, 

which  enclofes  and  lies  between  the  air  veficles  of 
the  lungs,  is  every  where  interfperfed  with  innu- 
merable fmall  ramifications  of  both  kinds  of  pul- 
monary vcfTcls,  viz.  of  the  pulmonary  artery,  and 
of  the  four  pulmonary  veins,  the  branches  of 
which  accompany  the  branches  of  the  bronchice, 
and  afterwards,  form  in  their  courfe,  by  an  im- 
mense number  of  divifions  and  fubfequent  anafto- 
mofes,  reticular  intertextures,  and  expanfiens  of  ex- 
treme fmenefs  and  fubtilty.  This  truly  aftonifhing 
reticular  tiiTue,  running  in  all  directions  through 

the 


OF  RESPIRATION.  IOi 

the  cellular  membrane,  fo  completely  furrounds, 
and  clofely  embraces,  the  cells  deftined  for  the 
reception  of  air,  that  the  whole  volume  of  blood, 
which  paffes  in  an  inceffant  round  through  the 
pulmonic  fyftem,  is  feparated  from  the  air  taken 
in  at  each  infpiration,  by  nothing  elfe  than  mem- 
branes (o  amazingly  fine  and  fubtle,  as  fcarcely  to 
be  equal  in  thicknefs,  (according  to  the  obferva- 
tions  and  calculations  of  Ilalesj,  to  the  one  thou- 
fandth  part  of  an  inch. 

§  "37- 

As  we  have  already  obferved,  that  each  indivi- 
dual ramification  of  the  bronchia;' has  appended  to 
it  its  own  peculiar  clufter  of  air  veficles  (§  135),  fo 
likewife  it  appears,  that  to  every  individual  velicle 
of  each  duller  is  peculiarly  appropriated  its  own 
fyftem  of  fmall  blood  vefTels,  the  minute  rami- 
fications of  which  communicate  very  frequently 
with  one  another,  forming  thofe  fiirprifmg  reticu- 
lar tifllies  aleady  fpoken  of,  but  fcarcely  appear  to 
anaftomofe,  in  any  degree,  with  the  fmall  blood- 
veffeU  of  the  adjacent  cl Lifters.  That  this  is  a 
truth  we  are  taught,  if  I  am  not  deceived,  as  well 
from  microfcopical  obfervations  made  on  the  lungs 
of  living  frogs  and  ferpents,  as  from  more  minute 
and  fuccefbful  injections  of  the  lungs  of  human 
fubje&s :  the  fame  thing  is  alfo  further  evidenced 
by  certain  pathological  phenomena  which  may  be 
G  3  obferved 


i ©2  OF  RESPIRATION. 

obfervcd  in  vomica,  and  other  fimilar  topical  affec- 
tions of  the  pulmonic  fyftem. 

§  138- 

It  is  neceffary  to  mention  alfo,  in  the  laft  place, 
that  fmgular  and  ftriking  apparatus  of  lymphatic 
veffels,  which  fpreads  and  appears,  in  a  more  parti- 
cular manner,  on  the  external  membrane  by  which 
the  lungs  are  inverted.  To  this  apparatus  of  vef- 
fels  belongs  that  numerous  affemblagc  of  lympha- 
tic or  conglobate  glands,  which,  though  of  a  quite 
different  and  diftinct  order,  are  neverthelcfs  com- 
monly confounded,  through  miftake,  with  thofe 
glands  in  their  neighbourhood,  which  are  called 
bronchialcs. 

§  *39- 

The  thorax,  in  which  the  lungs  are  fecurely 
tnclofed,  has  for  its  foundation  or  ikeleton,  bones 
and  cartilages,  arranged  and  dilpofed  fomev  hat 
like  the  walls  or  fides  of  a  cave.  Though  this 
bony  cavity,  taken  together  as  an  entire  whole, 
be  to  a  considerable  degree  firm  and  fteady,  3  t 
mod  of  its  parts  are  fo  pliant  and  moveable,  as  to 
be  well  adapted  for  the  performance  of  thofe  mo- 
tions which  the  bufinefs  of  refpiration  requires. 

This  pliability,  or  facility  of  motion  is  particu- 
larly obfervable  in  fix  pairs  of  the  true  ribs,  which 

being 


OF  RESPIRATION.  103 

being  placed  beneath  the  fuperior  and  fird  pair, 
are  more  moveable  in  proportion  as  their  fituation 
is  lower ;  or  their  aptitude  for  motion  is  com- 
mcofurate  with  the  fuperior  length  of  their  bodies, 
and  cartilaginous  appendices,  which  connect  them 
to  the  mar-ins  on  each  fide  of  the  fternum,  by  a 
fpecies  of  articulation  called  amphiarthrojis, 

§    140. 

Between  the  edges  of  thofe  rib?  lie  two  drata 
of  intercoflal  mufcles,  the  fibres  of  which  aifume 
indeed  and  pLirfue  different  directions,  but  which, 
neverthelefs,  co-operate  in  their  action  in  pro- 
ducing the  fame  motion  in  the  parts  to  which 
they  are  attached. 

Acrcfs  the  bafis  or  inferior  part  of  the  whole 
of  this  cavity  the  diaphragm  is  ftretched,  fomewhat 
in  the  form  and  direction  of  an  arch.  This  is  a 
mufcle  worthy  of  particular  attention,  and,  to  ufe 
the  words  of  Haller,  next  in  importance  to  the 
heart  itfclf ;  its  parts  appear  to  depend  chiefly  on 
the  phrenic  nerve  for  their  fitnefs  to  co-operate  in 
the  function  of  refpiration,  as  was  long  fince  de- 
monftrated  by  the  celebrated  live-diiTeclions  of  the 
immortal  Galen. 

The 


xo4  OF  RESPIRATION. 

The  diaphragm  alternates  for  the  mod  part,  by 
an  antagonizing  motion,  with  the  mufcle>  of  the 
abdomen,  efpecially  with  the  external  and  internal 
oblique,  and  the  tranjverfe  mufcles. 

§  141. 
The  thorax  thus  formed  and  finiflied  is,  in  the 
living  human  fubject  after  birth,  alternately  dilat- 
ed at  the  time  of  each  infpiration,  and  contracted 
again  to  its  former  dimenfions  in  every  fubfequcnt 
act  of  expiration. 

In  infpiration,  the  enlargement  of  the  tho- 
racic cavity  extends,  in  a  more  efpecial  manner, 
literally  and  downwards,  fo  that  the  bodies  of 
thofe  ribs  of  which  we  have  particularly  fpoken 
(§  139)  are  elevated,  and  their  inferior  margins 
or  edges  turned  in  fome  degree  outwards  ;  while, 
at  the  fame  time,  the  arch  of  the  diaphragm  is 
ibmewhat  depreffed,  and  brought  nearer  to  the 
portion  of  a  plain,  or  level  furface. 

But  as  to  what  is  boldly  afTerted  of  thefternum, 
viz.  that  its  inferior  end  is  at  the  fame  time  pro- 
truded forward,  this  is  a  phenomenon  which  I 
mull  confefs,  I  have  never  been  able  to  obferve  in 
the  tranquil  and  unmolefted  refpiration  of  a  healthy 

fop, 


OF  RESPIRATION1.  105 

This  alternate  motion  of  the  thorax,  which  in 
a  healthy  fubject  is  indeed  performed  fpontane- 
onfly  and  without  effort,  is  uniformly  continued 
from  the  moment  of  birth  to  the  extinction  of  life, 
for  the  following  neceiiary  and  important  pur- 
pofes,  namely,  that  the  lungs  themfcivrs  may,  by 
a  fimiiar  viciflitude  of  motion,  be  expanded  for  the 
free  admiffion  and  convenient  reception  of  the  air 
we  infpire,  and  again  contracted  in  order  that  the 
fame  may  be  forthwith  expelled. 

§   H3- 
For  man,  together  with  all  other  warm  blooded 

animals,  is  prevented,  by  abfolute  neceiiity,  from  a 
lengthy  retention  of  the  air  which  he  infpires  ;  he 
is  obliged,  after  a  very  fhort  period  to  difcharge  it 
again,  and  exchange  it  for  a  frefli  fupply  of  this 
vital  pabulum  ox  food,  as  the  air  has  been  termed, 
even  from  the  mod  remote  ages.  It  appears  in- 
deed from  the  mofl  common  obfervation,  that  the 
air  which  is  infpired  and  retained  any  time  in  the 
lungs,  however  great  may  have  been  its  original 
purity,  fuffers,  in  a  very  (hort  time,  fuch  remark- 
able changes  as  afFecl  it  with  the  mod  obvious 
contamination,  and,  unlefs  it  be  fpeedily  renewed, 
render  it  wholly  unfit  to  be  any  farther  employed 
in  the  important  procefs  of  respiration. 

S  144. 


106  OF  RESPIRATION. 

§  '44- 

Enquiries  have  been  inftirutcd  for  the  purpofe 
of  afcertaining  the  nature  of  thofe  changes  which 
the  air  we  infpire  undergoes  in  our  lungs.  Such 
changes  certainly  do  not  arife,  as  was  formerly 
believed,  from  the  lofs  of  any  myfterious  principle 
of  elafticity,  which  refides  in  the  air,  but  are  evi- 
dently produced  by  a  decompofition  of  its  elemen- 
tary parts.  For  the  atmuipheric  air  which  we 
breathe  is  truly  an  aftonifhing  mixture  of  elemen- 
tary fubflances,  very  widely  different  from  each 
other  in  their  natures.  Not  to  mention  the  va- 
rious heterogenous  matters  which  this  neceffary 
fluid  contains  ;  fuch,  for  example,  as  the  aerial 
feeds  of  the  fmalleft  and  meft  fimple  plants,  the 
odorous  effluvia  arifing  from  numerous  bodies, 
volumes  of  dufl,  and  a  thoufand  other  fimilar  fub- 
flances, which  for  the  mod  part  float  in  the  at- 
mofphere.  Not  to  mention,  I  fay,  thefe  hetero- 
genous bodies  at  all,  the  air  which  we  breathe 
always  contains  aqueous  exhalations  in  larger  or 
(mailer  quantities,  and  is  alfo  more  or  lefs  charged 
with  the  matters  of  electricity  and  magnetifm. 
But  finally,  though  the  whole  of  the  foregoing 
fubflances  be  left  entirely  out  of  view,  yet  even 
then  the  air  of  our  atmofphere  does  not  conftll  of 
one  fimple  aeriform  fluid,  but  is  compofed  of  de- 
phlogiflic.ited,  phlogiidicate-,  and  fixed  airs. 

The 


OF  RESPIRATION.  107 

The  proportion  of  thofe  elementary  matters, 
efpecial'y  of  fuch  as  are  organic,  is  varied  ex- 
tremely from  diverfity  of  places,  and  by  the  nature 
of  the  bodies  which  exift  in  thefe  places.  It  is  in 
the  mean  time,  however,  the  common  eftimation, 
that  the  air  of  our  atmofphere  confifts  of  about 
ith  part  of  dephlogifticated,  Hths  of  phlogifti- 
cated,  and  £th  of  fixed  air. 

§  145- 
It  appears,  that  at  each  infpiration,  (in  which 
an  adult  fubject,  breathing  in  a  quiet  and  tranquil 
manner,  draws  in  about  30  cubic  inches  of  air,)  a 
fourth  part  of  the  dephlogifticated  air  is  decom- 
pofed,  and,  in  a  great  meafure,  exchanged  for 
phlogifticated  and  fixed  airs ;  fo  that  the  expired 
fluid,  being  received  into  a  proper  veflel,  extin- 
guishes flume  or  coals  when  immerfed  into  it,  pre- 
cipitates lime  from  the  water  which  fufpends  it, 
and  far  exceeds  atmofpheric  air  in  its  fpecific  gra- 
vity, &c. 

§  14-6. 
It  is  probable  that  the  igneous  parts  of  the  de- 
phlogifticated air,  i.  e.  thofe  parts  fuited  to  favour 
the  procefs  of  combufticn,  being  fet  at  liberty  by 
the  decompofltion  which  takes  place  in  the  lungs, 
enters  the  arterial  blood,  and  is  thus  diilributed 
throughout  the  whole  body  j  while,  on  the  other 

hand, 


tc8  OF  RESPIRATION. 

hand,  the  bafis  of  fixed  air  is  carried  back,  along 
with  the  phlogifticated  and  venous  blood,  to  the 
right  fide  of  the  heart,  and  thence  (as  the  an- 
cients were  pleafed  to  exprefs  themfelves)  ex- 
creted through  the  lungs  like  foot. 

The  more  florid  dye  of  the  arterial  blood,  the 
more  obfeure  colour  of  the  venous,  and  the  fimili- 
tude  of  colours  imparted  to  both  kinds  of  blood, 
when  expofed  to  the  aclion  of  thofe  fpecies  of  air 
now  under  our  confideration  (§  16),  are  circum- 
ftances  very  much  in  favour  of  the  preceding 
opinions. 

In  a  fcetus  which  has  never  yet  received  vital 
air  into  its  own  pulmonic  fyftem,  there  is  in  general 
lefs  difference  between  the  arterial  and  venous 
blood,  than  in  an  adult  fubjeft,  in  whom  the  pro* 
cefs  of  refpiration  has  already  taken  place. 

After  the  infant  is  born,  the  new  fenfation,  ex- 
cited by  the  contact  of  an  unufual  element,  in  an 
animal  which  had  hitherto  led  an  aquatic  life,  and 
the  application  of  various  other  flimuli  altogether 
new,  appear  to  afford  us  a  happy  clue  for  explain- 
ing the  new  motions  which  at  that  period  take 
place  in  the  body,  more  especially  the  dilatation 
of  the  thorax  and  the  firft  aft  of  infpiration. 

When 


OF  RESPIRATION.  109 

When  the  lungs  are  dilated  by  this  firft  complete 
a&  of  infpiration,  a  new  paflage  is  thus  opened 
through  them  for  the  blood,  fo  that  this  fluid  is 
ever  after  diverted  from  the  umbilical  vefTels  to 
the  thorax. 

But  when  this  infpired  air  is,  by  that  decompo- 
fnion  of  its  elementary  parts,  of  which  we  have 
already  fpoken,  rendered  both  noxious  and  trou- 
blefome  to  the  lungs,  I  afcribe  to  the  mod  fimple 
prefervative  efforts  of  nature,  the  immediately  fub- 
fequent  motion,  by  which  this  poifonous  mephitis 
is  exfpired,  and  profitably  exchanged  for  a  frefh 
fupply  of  the  foftering  pabulum  of  life. 

From  all  the  foregoing  circumftances,  taken 
collectively,  (efpeciaily  if  we  attend  to  the  great 
influence  of  refpiration  on  the  circulation  of  the 
blood,  as  demonftrated  by  the  well  known  experi- 
ment of  Hooke),  we  are  furnifhed  with  a  much 
better  explanation  of  the  celebrated  problem  of 
Harvey,  than  has  yet  been  given  by  moft  of  the 
other  reiterated  labours  of  phyfiologifts,  who  have 
attempted  to  folve  that  difficulty. 


SECT. 


no  OF  VOICE  AND  SPEECH. 

SECT.     XII. 
OF  VOICE  AND  SPEECH. 

§  >4«- 


1  HE  leading  function  of  refpinuion 
has  been  already  the  fubject  of  our  confident) on. 
We  will  fpeak,  in  another  place,  of  the  part  which 
this  fublime  procefs  acts,  in  blending  and  intimately 
uniting  the  chyle  with  the  blood,  and  alfo  of  the 
fervices  which  it  renders,  in  a  variety  of  ways,  to 
almolt  the  whole  clafs  of  natural  functions,  (§  63. 
1 12.)  We  now  proceed  to  confider  its  other  ufes 
in  the  animal  economy. 

The  firfr.  object  or  phenomenon  which  attracts 
our  attention,  in  this  invefligation,  is  the  Voice, 
which  belongs  to  the  human  fubjecT:  after  birth, 
and  evidently  proceeds  from  the  lungs,  as  was 
long  fince  very  juftly  obferved  by  Ariftotle,  who 
faid,  that  no  animals  are  vocal,  i.  c.  poITefs  the 
power  of  emitting  found,  but  fuch  as  breathe 
through  lungs.  For,  by  the  denomination  of  voice, 
we  properly  defignate  that  found  formed,  by  means 
of  the  exfpired  air,  in  the  larynx,  which  is  a  fmall 
apparatus  or  machine  of  the  mod  exquifite  {frac- 
ture, placed  on  the  top  of  the  wind-pipe  or  afpera 

arteria, 


OF  VOICE  AND  SPEECH.  1 1 1 

arteria,  fomewha:  like  a  capital  on  the  furamic  of 
a  column. 

§  H9- 
This  fmall  machine  is  compofed  of  various  car- 
tilages joined  together  fomewhat  after  the  form  of 
a  capfula  or  caiket.  Thefe  cartilages  are  furniihed 
with  a  great  and  truly  admirable  apparatus  of  muf- 
cles,  in  confequence  of  which,  not  only  the  whole 
are  rendered  fit  for  motion  collectively,  but  fome 
of  them  are  alfo  enabled  to  move  individually  and 
alone,  according  to  the  different  variations  abouc 
to  be  produced  in  the  voice. 

§    '50- 
That  part  which  is  more  particularly  engaged  hi 

the  immediate  generation  of  the  voice  is  die  glottis, 
a  very  narrow  paffage  leading  into  the  wind-pipe 
from  above,  to  which  is  prefixed,  or  applied  as  a 
lid,  a  minute  cartilage  called  the  epiglottis.  That 
found  is  produced  by  the  air  expelled  from  the 
lungs,  finking,  in  a  proper  direction  and  with  due 
force,  agairft  the  edges  of  this  llrait  paffage,  is  a 
matter  too  plain  to  admit  of  a  doubt. 

§    i5r- 
Controverfies   have   exitted   on   the  fubjeel  of 

thole   changes   that   take  place  in  the  glottis,   by 

which  the  modulations  of  the  voice  are  produced, 

namely, 


112  OF  VOICE  AND  SPEECH'. 

namely,  Whether  this  cartilaginous  part  be  alter- 
nately expanded  and  contracted,  as  was  the  opi- 
nion of  Galen,  and  afterwards  of  Dodart?  or, 
Whether  the  variations  of  the  voice  do  not  rather 
depend  on  the  tenfion  and  relaxation  of  its  liga- 
ments, as  war.  held  by  Ferrein  ? 

The  latter  of  thofe,  therefore,  compared  the 
primary  organ  cf  the  voice  to  a  violin,  the  former 
to  TLJlute — i.  e.  the  onefet  of  difputants  conceived 
it  to  emit  found  on  the  principles  of  a  corded^  the 
other  on  thofe  of  a  wind,  injirwnent  of  mufic. 

From  a  faithful  collection,  and  impartial  confi- 
deration,  of  all  the  arguments  which  have  been 
advanced  on  this  contefled  point,  we  are  of  opi- 
nion, that  both  kinds  of  changes  do  actually  take 
place  in  the  glottis  when  employed  in  the  emiiTion 
of  found  ;  but  we,  neverthelefs,  believe,  that  the 
principal  and  mod  important  of  thofe  changes  de- 
pend on  and  arife  from  the  tenfion  of  the  liga- 
ments, more  efpecially  of  the  thyreo-arytonoidei 
inferiores  (which  appear  to  have  been  the  vocal 
cords  of  Ferrein. 

§    152. 

That  all  this  mobility  of  the  glottis,  of  whatever 

kind  it  may  be,   is  influenced  and  wholly  directed 

by  the  numerous  ir.ufcles  which  belong,  and  are 

1  attached, 


OF  VOICE  AND  SPEECH.  ir3 

attached,  to  the  larynx,  may  be  fully  eftablifhed 
by  the  following  beautiful  experiment,  viz.  It  the 
recurrent  or  wandering  nerves  (as  they  are  termed) 
be  either  fecured  in  light  ligatures,  or  completely 
cut  afunder,  the  voice  of  the  animals  fubjec>*d  to 
fuch  experiments,  will  be  in  the  former  cafe,  ren- 
dered extremely  weak  and  low,  and  in  tne  latter, 
entirely  deftroyed. 

§  153- 
The  faculty  of  ichifiling  belongs  in  common 
both  to  the  human  fpecies,  and  to  fmall  birds  of 
note.  To  qualify  them  for  this,  fmging  birds  are 
furniflied  with  a  bifurcated  larynx  at  each  extre- 
mity of  the  afpera  artcria.  But  though  human 
fubjects  be  fupplied  with  only  one  plain  and  fimple 
larynx,  yet  they  learn  to  imitate  thofe  fmall  ani- 
mals, as  appears  to  me,  by  a  co-arftion  or  pucker- 
ing up  of  their  lips. 

%  154- 
But  fong,  which  is  compofed  of  fpeech  and  a 
harmonious  modulation  of  the  voice,  I  would  con  - 
fider  as  peculiar  to  man  alone,  and  as  conftituting 
the  leading  prerogative  of  his  vocal  organs.  The 
faculty  of  whittling  is,  as  already  obferved,  a  part 
of  the  birth-right  of  birds  :  a  numerous  train  of 
the  feathered  race,  and  fometimes  even  dogs  them- 
felves,  have  a!fo  been  taught  to  pronounce  a  va- 
tQL.  i.  H  riety 


**4  OF  VOICE  AND  SPEECH. 

riety  of  words.  But  I  doubt  extremely  indeed,' 
whether  any  brute  animals  have  ever  yet  polfcffed 
a  faculty  of  true  an.i  genuine  fong ;  whereas,  on 
the  other  hand,  I  believe  there  fcarcely  exifts  a 
a  nation  fo  barbarous,  where  fong  does  not  very 
generally  prevail. 

§  *55- 
Speech  iifelf  is  a  peculiar  modification  of  the 
voice,  chiefly  by  the  aid  of  the  tongue,  but  par- 
tially alfo  by  that  of  the  lips,  the  teeth,  the  palate, 
and  by  the  further  afnftance  of  the  nofe,  combined 
into  the  formation  of  words. 


Hence  the  difference  between  voice  and  fpeeck 
appears  very  obvious  and  plain  :  the  firlt  is  evi 
dently  formed  in  the  larynx  itfelf ;  wnereas  the 
latter  is  effected  by  the  Angular  mechanifm  of  th 
other  organs  already  menroned.  It  is  but  ju 
and  proper,  however,  to  obferve,  that  this  laft 
pofition  is  not  capable  of  univerfal  application,  as 
there  are  a  few  nations  (of  which  the  Sinenfians 
may  fcrve  as  an  example),  among  whom  their  al- 
moil  homonymous*  words  are  diftinguiftied  only 
by  a  varied  modulation  of  the  voice  itfelf. 


1 


*  A  word  is  faid  to  be  homonymous,  when  it  is  highly- 
equivocal,  or  ufed  indifcriminately  to  reprefent  a  difcordant 
variety  of  obje&s  or  things. 


OF  VOICE  AND  SPEECH.  *ti§ 

But  further,  voice  belongs  in  common  to  brutes 
as  well  as  to  man  ;  it  is  poffcfled  alfo  by  the  new- 
born babe,  nor  is  it  wholly  denied  to  fuch  unhap- 
py infants  as  have  patted  their  lives  amidfr  the 
haunts,  and  in  the  gloomy  fociety,  of  wild  beads, 
nor  even  to  thofe  that  have  been  born  without  the 
fenfe  of  hearing.  But  fpeech  is  not  acquired  till 
after  the  cultivation  and  exercife  of  reafon ;  it 
conftitutes,  therefore,  no  lefs  than  that  operation 
of  the  mind  itfelf,  a  characteriftic  privilege,  and 
diftin&ive  prerogative  between  man  and  the  reft 
of  the  animal  kingdom.  To  ferve  all  the  pur- 
pofes,  and  anfwer  all  the  demands  of  brutes,  that 
inftincT:  with  which  nature  has  beneficently  fupplied 
them,  is  completely  adequate  ;  of  this  inftinft, 
however,  man  h  deftitute,  as  alfo  of  fuch  other 
aids  and  individual  powers  as  might  enable  him  to 
preferve  and  fuftain  life  by  his  own  folitary  exer- 
tions ;  he  is  therefore  kindly  furnifhed  with  the 
prerogatives  of  reafon  and  fpeech^  by  means  of 
which,  embracing  the  advantages,  and  difcharg- 
ing  the  duties,  annexed  to  a  focial  flate,  he  is  able 
both  to  difclofe  his  own  wants,  and  relieve  thofe 
•f  his  fellow  creatures. 

That  truly  admirable  mechanifm,  by  means  of 

which  fpeech  and  the  pronunciation  of  letters  are 

H  2  effected, 


i 


ji6  OF  VOICE  AND  SPEECH. 

effe&ed,  has,  fince  the  celebrated  refearches  of 
that  paradoxical  character,  Franc.  Mcrcur.  Hel- 
mont,  been  very  much  illuftrated  and  explained 
by  further  and  later  enquiries,  efpecially  thofe  of 
Jo.  Wallis  and  Conr.  Ammanus. 

That  dhifion  of  the  letters  by  Ammanus  into 
I.  Vowels,  II.  Semivowels,  and  III.  Confonants, 
is,  of  all  others,  by  far  the  mod  fimple  and  na- 
tural. 

I.  Vowels  he  again  divides  into  Jimple,  as  a,  e,  i, 
y,  0,  u9  and  mixed,  as,  a,  5,  ii. 

II,  Semivowels  arc  themfelves  either  nafals, 
fuch  as,  m9  ?i,  ng,  (i.  e.  n  placed  before  g  in  the 
German  language)  ;  or  Orals  (otherwife  called 
Unguals')  fuch  as,  r,  /. 

III.  Finally,  Confonants  he  divides,  ift,  into  the 
Sibilantes  or  hijfing  (i.  e.  into  thofe  confonants  the 
pronunciation  of  which  can  be  continued  for  an 
indefinite  length  of  time).  Thefe  are  h,  g,  ch,,  s, 
fch,  f,  v,  ph. 

2dly,  Explojive,  as,  k,  q,  d,  /,  b,  p,  and 

3dly,  Double  (or  Compound),  fuch  as,  x,  z. 

S   '57- 


OF  VOICE  AND  SPEECH.  u7 

S  iS7- 

Finally,  It  yet  remains  to  mention  certain  other 
modifications  of  the  human  voice,  which  ufually 
occur  as  fymptoms,  or  figns  of  either  particular 
pafIions  of  the  mind,  or  more  violent  affections  of 
the  organs  of  refpiration.  The  greater  part  of 
thefe  modifications  of  the  voice,  fuch  for  example, 
as  laughing  and  crying,  appear  to  belong  exclu- 
fively  to  the  human  race. 

§  iS8. 

Mod  of  the  modifications  which  immediately 
follow,  are  connected  together  by  fuch  a  powerful 
kindred  alliance,  that  one  of  them  is  not  unfre- 
quently  obferved  to  pafs  into  another.  It  mufl  be 
alfo  further  obferved,  that  the  greater  part  of 
them  do  not  always  afTume  and  exhibit  the  fame 
uniform  appearance,  &c. 

To  fpeak,  however,  in  general  terms,  in  the 
aft  of  laughing,  exfpirations  fhort,  interrupted,  and 
in  fome  meafure  broken,  follow  each  other  in 
quick  fuccefHon. 

Crying  produces  deep  infpirations,  which  fud- 
denly  alternate  with  lengthy  exfpirations  fre- 
quently interrupted  and  broken. 

H  3  Sighing 


n3  OF  VOICE  AND  SPEECH. 

Sighing  confifts  in  a  lengthy,  full,  and  flrong  in- 
fpiration, and  afubfequent  flow  exfpirarion,  which 
is  not  unfrequendy  accompanied  with  fomewhat 
of  a  groan. 

Coughing  is  produced  by  quick  and  fonorous 
exfpirations  fucceeding  a  deep  infpiration. 

Sneezing  is  a  more  violent  and  fomewhat  con- 
vulfive  exfpiration,  which  had  been  preceeded  by 
a  fhort  and  forcible  infpiration. 

The  Hickup  on  the  other  hand  confifts  entirely 
of  a  fingle  infpiration,  fonorous,  exireme\y  fudden, 
and  at  the  fame  time  of  a  convulfive  nature. 

The  prefent  feems  a  very  fuitable  occafion  to 
fpeak  of  the  phenomenon  of  yawning,  which  con- 
fifts in  a  full,  flow,  and  lengthy  infpiration,  -fuc- 
ceeded  again  by  a  fimilar  exfpiration,  while,  at 
the  fame  time,  the  jaws  are  drawn  fo  very  widely 
afunder,  that  the  air  which  is  received  into  the 
expanded  fauces  can  enter  with  cafe  the  Eujia- 
chean  tubes.  One  thing  peculiar  to  this  pheno- 
menon is,  its  being  extremely  contagious,  i.  e.  it 
very  readily  excites  to  imitation :  the  caufe  of  this 
js,  without  doubt,  to  be  fought  for  in  the  remem- 
brance of  the  agreeable  fenfatious  produced  at  a 
former  time,  by  the  languid  operation  of  yawning. 

SECT, 


OF  ANIMAL  HEAT.  n^ 

SECT.    xin. 

OF  ANIMAL  HEAT. 

§     159. 

IT  is  worthy  of  obfervation,  that  man  in 
a  living  ftate,  together  with  the  other  fubje&s  be- 
longing to  the  clafs  Mammalia,  as  vt  ell  as  the  whole 
feathered  race,  are  diftinguifhed  from  the  reft  of 
the  animal  kingdom  by  this  peculiarity,  that  the 
native  heat  of  their  bodies  far  exceeds,  in  degrees 
of  temperature,  the  ufual  heat  of  the  medium  or 
element  in  which  they  live.  With  refpeft  to  man 
himfelf,  it  is  however  to  be  remembered,  that  he 
appears  to  be  inferior,  in  the  heat  of  his  fyftem, 
to  thofe  other  kinds  of  animals  we  have  juft  men- 
tioned. Thus,  in  our  climate,  the  heat  of  the 
human  body  generally  ftands  at  about  the  96th 
degree  of  Fahrenheit's  fcale,  whereas,  in  other 
animals  belonging  to  the  clafs  Mammalia,  the  vital 
[  temperature  very  confiderably  exceeds  this  point, 
while  it  afcends  ftrll  higher  in  individuals  of  the 
feathered  tribes. 

§    1 6a. 

Indeed,  the  degree  of  native  heat  poffefTed  by  a 

healthy  perfen  is  fo  conftant  and  uniform,  that  in 

H  4  general^ 


ja#  OF  ANIMAL  HEAT. 

general,  (provided  we  make  allowance  for  the 
ftate  of  health  peculiar  to  each  individual),  its 
range  will  include  but  a  very  few  degrees  of  the 
thermometer,  whether  the  fudject  be  expofed  to 
the  inclemencies  of  the  mod  rigorous  climate,  or 
placed  beneath  the  fervors  of  a  tropical  fky.  For 
the  opinion  formerly  delivered  by  Boerhaave,  that 
man  has  not  a  power  of  exifting  in  a  medium  of 
fuch  a  nature  as  exceeds  in  temperature  the  native 
heat  of  his  own  body,  has,  fince  the  famous  ob- 
fervations  of  that  illuflrious  traveller  and  former 
governor  of  Georgia,  H.  Ellis,  been  refuted  by  a 
great  number  of  characters  learned  in  the  fcience 
of  phyfiology,  and  the  reverfe  completely  demon- 
flrated  and  eftablifhed  by  experiments  well  adapted 
to  the  nature  of  the  fubjecL  In  this  particular, 
indeed,  appears  to  confift  one  of  the  great  prero- 
gatives of  man,  that  imprifoned  and  confined  to 
no  one  climate  or  zone  of  the  earth,  he  is  able  to 
pafs  his  life  in  any  feclion  of  the  immenfe  globe 
we  inhabit,  and  is  free  to  fix  his  habitation  either 
beneath  the  rigors  of  Hudfon's  ftormy  channel, 
where  the  quickfilver  pafTes  fpontaneoufly  to  a 
ftate  of  complete  congelation,  am  id  ft  the  tempefts 
of  Nova  Zembla,  or  in  the  bofom  of  thofe  glaring 
folar  fires,  which  fcorch  the  glowing  ihores  of  the 
Senegal, 

§  161. 


OF  ANIMAL  HEAT.  |(j 

§  161. 

We  proceed  now  to  enquire  into  the  origin  and 
fource  of  that  aftonifhing  fire,  which  minutely 
pervades  our  bodies,  and  uniformly  fupplies  them 
with  their  neccflary  degrees  of  warmth.  To  pafs 
in  filence  over  the  vifionary  conjectures  of  the 
ancients  on  this  fubjeft,  fome  of  the  moderns  have 
attempted  to  derive  animal  heat,  with  all  its  phe- 
nomena, from  the  matter  of  electricity  and  the 
nerves,  others  from  the  attrition  generated  by  the 
circulation  of  the  blood,  others  from  the  recipro- 
cal friclion  between  the  folid  elementary  parts  of 
living  animals,  while  others,  again,  have  embraced 
and  defended  different  opinions. 

§  162. 
But  all  thofe  hypothefes  are  embarraffed  with 
infurmountable  difficulties,  whereas,  on  the  other 
hand,  the  utmofl  fimplicity,  and  an  entire  cor- 
refpondence  to  the  phenomena  of  nature,  combine 
in  recommending  and  confirming  that  doclrine,  in 
which  the  lungs  are  confidered  as  t\ic  focus  ox  fire  - 
■place  where  animal  heat  is  generated,  and  the  de- 
phlogifticated  part  of  the  air  which  we  breathe, 
as  the  fuel  that  fupports  the  vital  flame.  That 
juftly  celebrated  character,  Jo.  Mayow,  fketched 
out,  formerly,  the  leading  traces  and  firft  great 
outlines  of  this  doclrine,  which,  in  our  times,  has 
been   greatly   improved,   extended,   and   farther 

elucidated, 


122  OF  ANIMAL  HEAT. 

elucidated,  by  the  labours  of  the  illuftrious  Craw- 
ford. 

The  whole  drift  and  tenor  of  Crawford's  theory 
obvioufly  refults  in  this,  that  refpiration,  no  lefs 
than  combu/lion,  belongs  to  fuch  procefTes  as  are 
called  phlogiftic  ;  in  which  the  phlogifton  refiding 
in,  and  conftituting  a  part  of,  our  bodies,  is  ex- 
pelled by  the  acceflion  of  free  or  fcnfiblc  heat, 
(which  ought  to  be  carefully  diftinguifhed  from 
heat  exifting  in  a  fixed  or  latent  date.) 

For  phlogifton  and  the  matter  of  heat  are  ele- 
ments of  fuch  contrary  and  oppofite  natures,  that 
the  greater  quantiry  of  the  one  our  bodies  at  any 
rime  contain,  the  lefs,  at  the  fame  time,  is  their 
proportion  of  the  other ;  thus,  fixed  air,  for  ex- 
ample, is  not  fuppofed  to  contain  more  than  aVth 
part  of  the  quantity  of  the  matter  of  heat,  which 
belongs  to  an  equal  weight  of  atmofpheric  air,  &c. 

But  it  appears,  from  experiments,  that  atmo- 
fpheric air  has  a  ftronger  affinity  to  phlogifton 
than  to  the  matter  of  heat,  fo  that  it  unites  itfelf 
with  the  greateft  readinefs  to  the  former,  while,  at 
the  fame  time,  it  fets  at  liberty  the  latter,  which 
had  been  hitherto  held  in  a  fixed  and  latent  ftate. 

§  164. 


OF  ANIMAL  HEAT.  123 

§    164. 
When  we  come  to  apply  the  foregoing  por- 
tions and  principles  to  the  phenomena  of  refpira- 
tion,  it  appears  highly  probable,  that  animal  heat 
is  generated  by  a  procefs  of  a  fimilar  nature. 

For,  as  we  have  already  had  occafion  to  ob- 
ferve,  the  air  whicli  we  exfpire  differs,  in  a  very 
remarkable  degree,  from  wh;.t  we  had  immediately 
before  infpired  ;  being  deprived  of  its  igneous 
portion,  or  of  that  part  fit  for  contributing  to  the 
fupport  of  flame,  it  is  returned  highly  impreg- 
nated, on  the  contrary,  with  phlogifton  and  the 
bafe  of  fixed  air.     (§  146.) 

It  appear?,  therefore,  extremely  prcbable,  that 
the  igneous  portion  of  the  air  we  breathe  enters 
thofe  minute  blood-vefTels,  which  are  every  where 
difperfed  throughout  the  fubflance  of  the  lungs, 
and  feparated  from  the  air-veficles  themfelves  by 
nothing  more  than  fubtle  partitions  of  the  mod 
filmy  texture  (§  136)  ;  that  from  the  lungs  it  is 
conveyed  through  the  pulmonary  veins  to  the 
aorta,  from  whence  it  is  again,  by  means  of  the 
arterial  fyftem,  diftributed  throughout  every  part 
©f  the  body. 


During 


i24  OF  ANIMAL  HEAT. 

During  the  whole  cnurfc  of  this  minute  diftri- 
bution,  more  efpecially  while  in  the  extreme  ra- 
mifications of  the  veffels,  it  appears  to  be  ex- 
changed for  phlogifton,  which  it  every  where 
meets  with  in  confiderable  quantities.  This  phlo- 
giftic  principle,  being  thus  mixed  with  the  blood, 
and  occupying  the  place  juft:  evacuated  by  the 
mauer  of  heat,  is  conveyed  back,  by  means  of  the 
venous  fyftcm  to  the  right  fide  of  the  heart,  and 
from  thence  by  the  pulmonary  artery,  into  the 
lungs,  where,  agreeably  to  the  fe  laws  of  affinity 
which  we  juft  now  hinted  at,  it  is  immediately 
received  and  taken  up  by  the  volume  of  air 
recently  infpired.  In  confequence  of  the  acceifion 
of  this  quantity  of  ph'ogifton,  and  its  union  with 
the  air  contained  in  the  lungs,  a  frefh  portion  of 
the  element  of  fire  or  heat  is  fet  at  liberty,  which 
inflantly  enters  the  blood  and  is  thus  inccflantly 
diitributed  throughout  the  fyftem  in  the  manner 
aheady  defcribed. 

§  166. 

The  truth  of  this  theory  is  evidenced  by  thofe 
diverfnics  between  arterial  and  venous  blood,  to 
which  we  have  every  where  adverted.  It  is 
alfo  farther  evidenced  by  the  difference  between 
the  fpecific  heat  of  arterial,  and  that  of  venous 
blood  ;  thus  the  fpecific  heat  of  the  blood  con- 
tained in  the  arteries  is  to  that  of  the  blood  con- 
tained 


OF  ANIMAL  HEAT.  125 

tained  in  the  veins,  as  ill  to  10.  Finally,  as  an 
additional  evidence  of  the  fame  thing,  we  might 
mention,  in  the  feft  place,  that  ofcillatory  action 
exerted  by  the  fmalleft  order  of  blood  vefiels, 
which  was  the  fubjecl:  of  our  attention  on  a 
former  occauon. 

§    167. 

For  it  feems  altogether  probable,  that  thofe 
extremely  minute  ramifications  of  the  fanguiferous 
fyftem,  are  parts  of  fuch  utility  and  importance, 
that  in  proportion  as  their  action  is  itronger  or 
weaker,  a  correfpondent  increafe  or  diminution 
takes  place  in  that  exchan je  of  the  element  of  fire 
for  the  matter  of  phlogifton,  which  goes  conftanrly 
forward  in  the  body,  and  alfo  in  the  heat  of  the 
animal  uniformly  generated  by  fuch  exchange. 

Thofe  memorable  and  finking  phenomena,  from 
which  it  appears,  that  animal  heat  (if  indeed  the 
matter  be  determined  by  a  thermometer,  and  not 
trailed  to  the  fallacious  teft  of  f  nfation),  remains 
in  general  at  very  nearly  the  fame  precife  point  of 
temperature,  little  augmented  by  the  rummer's 
blaze,  little  diminimed  by  ths  winter's  blaft  ;  and 
further,  that  on  certain  occafions  the  heat  of  our 
bodies  is  even  increafed  in  confequence  of  an  im- 
merfion  in  cold  water — Thofe  phenomena,  I  fay, 
feem  to. demonstrate,  and  reduce  if  to  a  certainty, 

that 


ii6  OF  PERSPIRATION. 

that  according  to  the  variations  that  take  place  in 
the  temperature  of  the  medium  in  which  we  live, 
correfponding  diversities  immediately  follow  in  the 
aclion  of  the  fmallelt  vafcular  ramifications  of  our 
bodies.  From  this  Angularly  accommodating 
power,  refident  in  the  minute  extremities  of  our 
vafcular  fyftem,  it  follows,  that  on  being  expofed 
to  cold  (which  appears  to  aft  by  increafing  their 
tone),  they  are  immediately  enabled  to  exchange 
a  larger  quantity  of  the  principle  of  phlogifton  for 
the  igneous  pabulum,  and  thus  generate  a  higher 
degree  of  heat ;  whereas,  on  the  other  hand, 
they  are  obliged  to  exchange  a  much  /mailer  quan- 
tity, as  often  as  they  are  rendered  inactive  by  be- 
ing fubjected  to  the  influence  of  a  relaxing  and 
debilitating  medium. 


SECT.    XIV. 

OF  CUTANEOUS  PERSPIRATION. 

§     1 68. 

jO  various,  and  extremely  diverfined, 
are  the  functions  of  the  cutis,  with  which  the  hu- 
man body  is  inverted,  that  an  enumeration  and 
complete  account  of  the  whole  of  them  can 
fcarcely  be  comprehended  with  propriety  under 

one 


OF  PERSPIRATION.  127 

one  and  the  fame  head ;  they  would  appear  to 
be  more  fitly  arranged  for  confideration,  each  one 
under  that  clafs  of  aclions  to  which,  from  its 
nature  it  belongs. 

For,  in  the  firit  place,  the  cutis  is  the  organ  of 
touch,  of  which  we  will  fpeak  when  treating  of 
the  animal  functions. 

It  is  again  the  medium  or  inftrument  of  inhala- 
tion,  by  which  office  it  makes  a  part  of  the 
abforbing  fyftem  of  lymphatics ;  this  fhall  be  a 
fubject  of  further  confideration,  when  we  come 
to  take  a  view  of  the  natural  funclions. 

Finally,  It  is  the  laboratory  or  organ  of  perfpi- 
ration  alfo.  This  function  agrees  in  a  great 
variety  of  refpecls  with  the  procefs  of  refpiration, 
and  appears  therefore  to  be  introduced  with 
Sufficient  propriety  as  the  fubject  of  the  prefent 
fection. 

§    169. 

The  cutis  is  faid  to  confifl:  of  a  threefold  mem- 
brane, or  of  a  membrane  compofed  of  three 
laminae.  Thefe  laminas  or  layers  are  the  corium 
or  true  fkin,  lying  on  the  interior  fide,  the  cuticula, 
or  cuticle  making  the  exterior  covering,  and  the 
reticulum  (i.  e.  the  rete  mucofiwi),  which  is  fpread 

between 


128  O*  ANIMAL  HEAT. 

between  the  two  lamincc  juft  mentioned.    Of  each 
of  thefe  we  will  treat  feverally  and  in  order. 

§  170. 
The  cuticle,  or  epidermis,  forms,  as  juft  ob- 
ferved,  the  external  covering  to  the  whole  body  : 
It  is  thus,  from  its  fituation,  expofed  to  a  free  ac- 
ceflion  of  the  air,  the  immediate  contact  of  which 
element,  fcarcely  any  other  part  of  the  body  can 
bear  with  impunity,  even  in  a  found  date,  except 
the  enamel  of  the  teeth,  the  tubes  of  refpiration, 
and  the  alimentary  canal. 

§   I71- 
The  texture  of  the  epidermis  is  fimple  to  the 

utmofl  degree,  being  entirely  deftitute  of  veffels, 

of  nerves  and  of  pores.     This  texture,  though  on 

the  whole  fcarcely  organic,  is  neverthelefs  highly 

fingular  and  ftriking  ;  notwithftanding  its  femipel- 

lucid  and  tender  appearance,  its  tenacity  is  yet  fo 

very  confiderable  as  to  refill  effectually,   for   a 

great  length  of  time,  not  only  maceration,  but 

various  other  modes  of  generating  putrefaction. 

§    I72' 
The  origin  of  this  filmy  expanfion  is  as  yet  in- 
volved in  doubts  and  difficulties.     It  is    in  the 
mean  time,  however,  probable  that   it   fprings, 
along  with  the  fmall  bulbs  furrounding  the  roots 
4  of 


OF  PERSPIRATION.  12g 

of  the  hairs,  from  the  corium  or  true  fkin  expanded 
beneath  it :  that  this  is  the  cafe,  we  are  led  to  in- 
fer, from  the  myriads  of  minute  and  extremely 
tender  fibrils,  by  which  it  and  the  ikin  are  con- 
nected together. 

When  by  any  means  deflroyed,  ir  is  re-pro- 
duced aq;ain  with  greater  facility,  than  any  of  the 
©ther  folid  parts  of  the  human  body. 

§  l73- 
That  this  membranous  lamina  is  of  the  utmoft 

importance  in  the  economy  of  organized  bodies, 
is  inconteflibly  evinced  by  its  univerfal  prevalence 
throughout  both  the  animal  and  vegetable  king- 
doms. It  may  be  obferved  already  formed  even 
in  the  tender  embryo  itfelf,  at  fo  early  a  period  as 
the  third  month  after  the  time  of  conception. 

§  T74- 

Underneath  the  cuticle  is  expanded  a  thin  mu- 
cous membrane, which,  from  an  opinion  entertained 
refpe&ing  it,  by  its  celebrated  difcoverer,  is  called 
reticulum  Malpigbianum. 

This  reticulum  or  fubtle  net-like  expanfion,  ex- 
hibits the  habit  and  appearance  of  mucus,  ex- 
tremely eafy  of  folution  :  it  can  fcarcefy  in  any 
part,  except  in  the  fcrotum  of  ^Ethiopians,  be  fepa* 

vol.  i.  I  rated 


t2f  OF  PERSPIRATION. 

rated  entire  from  both  the  cuticle  and  true  {kin, 
and  thus  be  procured  in  the  form  of  a  genuine  and 
complete  membrane. 

The  part  now  under  confideration,  conftitutes 
the  primary  and  principal  feat  of  colour  in  the 
human  race.  In  all  men  the  true  iKin  is  fair  and 
ihining  ;  the  cuticle  alfo  is  femipellucid  and  whitifh 
in  all  nations,  except  the  inhabitants  of  ^Ethiopia, 
in  whom  it  is  more  dufkifh  and  obfeure.  But  in 
the  human  fubject  after  birth,  the  colour  of  the 
reticulum  mucofum  is  varied,  in  correfpondence  to 
the  diverfities  of  age,  mode  of  life,  climate,  and 
alfo  in  proportion  as  the  conftkution  is  more  or 
lefs  found. 

Thus,  for  example,  of  the  five  'varieties,  into 
which  the  human  race  appears  to  me,  to  be  with 
much  propriety  divided,  the  jirjl  has  the  reticu- 
lum more  or  lefs  whirifli.  This  defcription  in- 
cludes, befides  Europeans,  thofe  who  inhabit  the 
weft  of  Afia,  and  the  north  of  Africa,  together 
with  the  natives  of  Greenland  and  Efquimaux. 

idly,  In  the  fecond  variety,  which  includes  the 
inhabitants  of  all  the  other  parts  of  Afia,  the  reti- 
culum fomewhat  tawny,  inclining  to  an  olive 
cad. 

2>dlh 


OF  PERSPIRATION.  13 1 

%dty,  In  the  third,  which  embraces  the  inhabi- 
tants of  ^Ethiopia,  it  is  blackifh. 

Arthly,  In  the  fourth,  which  confifls  of  the  ab- 
origines of  America,  it  is  to  a  certain  degree  cop- 
per-coloured. 

5tbly,  Finally,  in  the  fifth,  which  comprehends 
the  inhabitants  of  all  the  South  Sea  iilands,  it  is 
more  or  lefs  tawny  or  brown. 

But  all,  and  each  one  of  thofe  varieties  of  co- 
lour, as  well  as  all  other  varieties,  by  which  man 
differs  from  man,  and  nation  from  nation,  appear 
to  be  fo  intimately  blended  together,  and  are  dif- 
pofed  to  run  into  each  other  with  fo  much  facility, 
that  it  feems  fcarcely  poffible  to  eftablifh  any  divi- 
fions  or  claifes  of  them,  but  fuch  as  are  plainly 
arbitrary. 

§  *76- 

The  Corhim  or  true  Jkin  itfelf,  to  which  the 
reticulum  and  epidermis  ferve  as  a  covering,  is  a 
membrane  of  a  peculiar  nature  ;  it  is  porous,  te- 
nacious, capable  of  valt  dilatation,  varied  in  its  de- 
grees of  thicknefs,  confiding  chiefly  of  condenfed 
cellular  membrane,  and  extremely  clofe  and  com- 
pact on  its  external  fuperficies  ;  it  is  more  lax  on 
she  internal  furface,  which,  (if  you  except  a  few 
I  2  re  ians 


OF  PERSPIRATION. 


regions  or  pares  cf  the  body)  (§  36.)  contains,  for 
the  moil  part,  a  certain  quantity  of  common  fat. 

§  177. 
Befides  nerves  and  abforbaits,  of  which  w«  will 
fpeak  particularly  on  a  future  occafion,  the  cor'tum 
or  true  fkin  is  alfo  plentifully  fupplied  with  innu- 
merable fmall  blood-vejfch ',  which  run  on  its  exte- 
rior furface,  and,  as  we  learn  from  a  fucceisful 
injection,  inveft  the  fame  with  reticular  expansions 
of  the  mod  clofe  and  fubtile  texture. 

§  178. 
Over  the  fame  exterior  furface  is  alfo  inter- 
fperfed  an  immenfe  afRmblage  of  fmall  febaccous 
follicles,  which  thoroughly  anoint  the  whole  cutis 
with  a  very  fubtle  and  limpid  oil,  of  fuch  a  nature 
as  not  to  be  eafily  evaporated  and  dried  up.  This 
fine  fluid  fhould  neither  be  confounded  with  the 
common  fiueat,  nor  yet  with  that  fetid  fuuflancc 
which  infefts  only  fome  particular  parts  of  the 
body. 

§   x79- 

Finally,  almofl  the  whole  of  the  true  fkin  is 
planted  with  hairs  of  various  kinds.  The  mo  ft 
numerous  and  abundant  of  thefe  are  very  fhort 
and  tender,  inclining  more  or  lefs  to  the  nature  of 
down  ;  of  hairs  which  fall  under  this  defcription, 

fcarcely 


OF  PERSPIRATION.  133 

fcarccly  any  part  of  the  body  is  destitute,  except 
the  eye-lids,  the  male  penis,  the  palms  of  the 
hands,  and  the  foles  of  the  feet.  But,  on  certain 
parts  of  the  body,  the  hairs,  being  deflined  for 
particular  ufcs,  grow  to  much  greater  lengths ; 
examples  of  this  we  have  in  the  hair  of  the  head, 
in  the  eye-brows,  in  the  eye-lafhcs,  the  hairs  in 
the  noflrils,  the  whiikers,  the  beard,  together  with 
fuch  hairs  as  grow  in  the  arm-pits,  and  about  the 
anus  and  parts  of  generation. 

§  180. 
In  general,  man  is  indeed  lefs  hairy  than  mod 
other  anim.ils  belonging  to  the  clafs  mammalia. 
A  difference  exifts,  however,  in  this  refpecl,  be- 
tween the  inhabitants  of  different  countries.  For, 
to  pafs  in  filcnce  over  thofe  nations  who  are  in 
the  daily  practice  of  plucking  out,  as  well  the 
beard,  as  the  hairs  which  appear  on  other  parts 
of  the  body,  there  are  not  wanting  certain  tribes, 
who  are  naturally  destitute  of  hair  ;  of  this  defcrip- 
tion  appear  to  be  the  Tungufos  and  the  Buratce. 
On  the  other  hand,  we  are  informed  by  travellers 
of  the  higheft  reputation  in  point  of  veracity,  that 
the  inhabitants  of  Nadigfda,  one  of  the  northern 
Kurilikian  Hlatids,  are  remarkable  for  the  unufual 
quantities  cf  hair  with  which  their  bodies  are  pro- 
tected. 


i34  OF  PERSPIRATION. 

§   III. 

Ne'ther  arc  the  varieties  fewer,  which  are  ex- 
hibited by  the  hair,  in  regard  to  length,  flexility, 
curlinefs,  and,  more  efpecially,  in  point  of  colour  : 
this  lad  property  depends,  in  general,  on  the  power 
of  climate,  on  age,  and  other  caufes,  which  exert 
their  influence  in  perfect  conformity  to  the  efla- 
Mifhed  laws  of  nature  ;  but  it  fometimcs  alfo  de- 
pends on  a  morbid  and  mifplaced  temperament,  as 
appears  to  be  the  cafe  in  the  white  natives  of 
./Ethiopia.  The  colour  of  the  hair  correfponds, 
for  the  mod  part,  to  that  of  the  eyes. 

§    182. 

There  is  alfo  a  further  peculiarity  in  the  direc- 
tion of  the  hairs,  on  certain  parts  of  the  body ; 
thus,  for  example,  on  the  vertex  or  crown  of  the 
head,  they  purfue  a  fpiral  direction  ;  on  the  pubes, 
they  diverge  and  point  upwards  ;  on  the  pofterior 
fide  of  the  arm,  they  look,  (as  on  the  ape,  and 
contrary  to  their  direction  on  the  fatyr),  towards 
the  elbow,  (that  is,  they  point  from  the  fhoulder 
downwards,  and  from  the  wrilt  upwards)  :  of  the 
directions  purfued  by  the  eye-brows  and  eye-la(hes, 
it  feems  unneceflary  to  fay  any  thing  on  the  pre- 
sent occafion. 

S  *fy 


OF  PERSPIRATION.  i3S 

§    *H 

The  hairs  originate  from  the  interior  furface  of 
the  true  (kin,  which  contains  a  quantity  of  fat : 
they  are  fixed  with  confiderable  firmnefs  in  each 
of  the  fmall  bulbs,  which  are  compofed  of  two  in- 
volucra  ;  the  external  involucrum  is  vafcular,  and 
oval ;  the  internal  is  cylindrical,  appears  continu- 
ous with  the  epidermis,  and  ferves  as  an  immedi- 
ate covering  to  thofe  elaftic  filaments  of  which 
each  individual  hair  is  itfelf  compofed,  and  which 
are  from  five  to  ten  in  number. 

S  l84- 
The  hairs  are  always  completely  befmeared  with 
an  oily  halirus,  and  are  almofl  incorruptible.  They 
appear  to  pc  fiefs  more  of  the  nature  of  original 
ele&rics  (or  of  eleclra  per  fe,  as  they  are  called), 
than  any  of  the  other  parts  of  the  body.  Their 
nutrition  is  extremely  fimple  and  eafy,  as  is  alfo 
their  re-produ&ion  after  having  fallen  off,  unlefs 
the  cutis  itfelf  be  labouring  under  fome  morbid 
affecYion. 

§  185- 

Befides  other  important  purpofes  which  thefe 

common  integuments  of  the  body  ferve,  they  are, 

in  a  particular  manner,  to  be  reckoned  among  the 

number  of  the  excretory  organs  of  the  fyflem  ;  by 

I  4  their 


i36  OF  PERSPIRATION. 

their  affifhmce,  in  this  point  of  view,  certain  foreign 
matters,  which  would  from  retention  prove  highly 
noxious,  are  hourly  eliminated  and  totally  removed 
from  the  general  volume  of  our  fluids. 

The  truth  of  the  above  pofition  is  fully  demon- 
ftrated  and  eftablilhed,  by  the  well-known  circum- 
ftance  of  miafmata  being  completely  removed  from 
the  fyftem,  under  the  appearance  of  exanthemata 
or  eruptions ;  it  is  alfo  proved  by  the  odours  of 
garlic,  mufk,  and  other  fubftances  taken  into  the 
body,  palling  by  the  fkin  ;  it  is  ftill  further  demon- 
ftrated  and  confirmed  by  the  procefs  of  fweating, 
and  by  other  phenomena  of  a  fimilar  nature. 

S  1 86. 
But  above  all,  thofe  excretory  paflages  convey 
off  a  certain  fluid,  which  is  called  the  perfpirable 
matter  of  Sa?iciorii(Sy  in  honour  of  that  moft  acute 
and  ingenious  philofopher,  who  infiituted  the  firfl 
ferics  of  rational  inquiries  for  the  exprefs  purpofc 
of  afcertaining  its  utility  and  importance. 

It  is  neceflary,  however,  to  obferve,  that  under 
this  appellation,  phyflologifh  commonly  defignate 
excrementitious  matters,  which,  if  not  oppojite,  arc 
at  lead  exceedingly  different,  in  their  natures,  and 
which  ought,  therefore,  to  be  diftinguifhed  from 
piich  other  with  the  utmcfl  accuracy  and  care  j  as 

the 


OF  PERSPIRATION. 


J37 


the   excretion  of  fweat,  for  inftance,   from  the 
genuine  matter  of  perfpiration* 

The  former  (/.  e.  the  fweaty  excretion)  is  a 
liquid  of  an  aqueous  nature,  faltifh  to  the  tafte, 
and  which  fcarcely  ever  iflues  fpontaneoufly  from 
the  healthy  body  when  in  a  ftaie  of  tranquility 
and  reft. 

But  the  latter,  (viz.  the  genuine  matter  of  per- 
fpiration),  of  which  alone  we  intend  to  treat  on 
the  prefent  occaficn,  is  an  aeriform  fluid,  perman- 
ently elaftic,  and  bearing  a  very  ftriking  refem- 
blance  to  that  which  we  exfpire  by  the  lungs. 

§  187.  ^ 
Like  that  elaftic  fluid,  it  is  highly  charged  with 
the  principle  of  phlogifton,  like  that,  it  precipitates 
quick-lime  from  the  water  in  which  it  was  fuf- 
pended,  and,  like  that,  it  is  alfo  unfit  both  for 
contributing  to  the  nourifhment  of  flame,  and  alfo 
for  fupporting  the  procefs  of  refpiration,  &c. 

§  188. 
The  quantity  of  this  fluid  that  exhales  from  the 
whole  fupcrficies  of  the  body  (which,  in  an  adult 
human  fubjccl  of  the  middle  fize,  amounts  by 
meafuremcnt  to  about  fifteen  fquare  feet)  can 
fcarcely  be  reduced  to  accurate  calculation. 

For, 


138  OF  PERSPIRATION. 

For,  that  the  fcales,  which  from  the  time  of 
San£torius  have  been  made  ufe  of  for  afcertain- 
ing  the  exact  weight  of  the  body,  are  not  well  cal- 
culated for  determining  the  precife  quantity  of  this 
elaftic  fluid,  may  be  eafily  undcrftood  from  what 
we  have juft  now  faid  refpecVing  the  different  fub- 
flances  whi:h  are  eliminated  from  the  fyftem  by 
the  flrin,  befides  the  true  matter  of  perfpiration. 

It  was  long  fince  difcovered,  that  the  nature 
and  quantity  of  prrfpiration  vary  extremely,  not 
only  in  different  pcrfons,  but  even  in  the  fame 
perfcns,  at  different  times.  It  feems  at  prefent, 
hovvever,  to  be  a  point  too  well  afcertained  to 
admit  of  a  doubt,  that  there  does  really  exift, 
with  refpedt  to  the  matter  perfpired,  a  national 
variety  and  peculiarity  ;  the  truth  of  this  we  con- 
fidently reft  on  what  has  been  faid,  by  aurhors  of 
the  higheft  veracity,  with  regard  to  the  lingular 
and  fpecific  odours  which  are  tranfpircd  through 
the  fkins  of  the  Caribeans,  of  the  Greenlanders, 
of  the  ./Ethiopians,  and  alfo  of  the  individuals  be- 
longing to  other  barbarous  tribes. 

§  .89. 

On  confidering  what  has  been  faid  with  refpeft 
to  the  vafcularity  obfervable  in  the  texture  of  the 
ikin  (§  177),  and  alfo  with  refpeft  to  the  analogy 
that  exifts  between  the  matter  of  perfpiration  and 

the 


OF  PERSPIRATION.  139 

the  air  we  expire  (§  1 87);  and  further,  on  confider- 
ing  what  has  been  advanced  refpe&ing  the  power 
and  influence  of  the  fmalleft  vafcular  ramifications, 
in  the  generation  of  animal  heat — to  him,  I  fay, 
who  carefully  weighs  and  attentively  confiders  all 
thefe  circumftances,  it  will  appear  extremely  pro- 
bable, that  there  exifts  a  ftrik'ng  fimilitude  indeed 
between  the  action  of  the  lungs  in  refpiration,  and 
that  of  the  fkin  in  the  procefs  of  perfpiration.  It 
will  appear  that  there  exifts  between  the  cutis 
and  lungs  a  reciprocal  confent  ;  fo  that  the  one 
may  be  fuppofed  capable  of  aflitling  and  fome- 
what  relieving  the  other,  and  even  of  fupplying 
its  place,  at  leafl  to  a  certain  degree,  in  cafe  of 
any  accident  or  derangement. 

§    190- 
In  fupport  of  this  opinion  we  can  adduce  the 
concurrent  teftimonies  of  a  variety  of  phenomena, 
obfervable   not   only  in  a  found,  but  alfo   in    a 
difeafed,  itate  of  the  fyflem. 

Some  of  thefe  phenomena  are,  for  example, 
thofe  leading  points,  in  which  the  human  fceius, 
as  well  as  that  of  the  other  animals  belon^imj  to 
the  clafs  mammalia,  differ  from  the  incubated 
chick,  or  the  young  of  the  feathered  tribes,  while 
yet  enclofed  in  the  farhtes  of  the  egg. 

A  further 


i4«  OF  PERSPIRATION. 

A  further  evidence  in  favour  of  the  fame 
opinion,  is  that  fingular  coldnefs  of  certain  parts 
of  the  body,  even  in  warm  blooded  animals,  (as 
in  the  nofes  of  clogs,  &c.)  which  appears  to  be 
refcrr-d  with  ftlfficient  propriety,  to  a  lefs  phlo- 
giftic  action  of  the  fmall  veflels,  with  which  thofe 
parts  abound. 

On  the  contrary,  from  an  encreafed  action  of 
the  minute  vcfT.ls  in  certain  parts  of  the  body,  we 
ex -lain,  with  the  lumoH:  fairnefs  and  facility,  a 
variety  of  morbid  fymptoms,  f.ich,  for  inilance,  as 
that  lingular  heat  and  flaming  in  the  palms  of  the 
hands,  which  occur  fo  frequem'y*  and  are  fo 
ftrikingly  obfervable  in  patients  labouring  under 
a  hectic  fever. 

With  regard  to  that  vicarious  action  of  which 
we  formerly  fpoke,  and  by  which  we  (aid  it  ap- 
peared probable,  that  the  functions  of  the  lungs 
and  cutis  lend  mutual  aid  and  afliftance  to  each 
other ;  that  fuch  an  action  does  unequivocally 
exift,  we  derive  fome  force  of  teftimony  from  thofe 
phenomena  in  pathology,  where  human  fubjeets, 
after  birth,  and  even  after  advancing  to  an  adult 
age,  having  their  lungs  almod  totally  deftroyed  by 
a  confumption,  or  highly  vitiated  by  fome  other 
contamination,  have  nevcrthelefi  furvived  fuch 
melancholy  misfortune?,  for  a  long  time,  and  in 

feme 


OF  PERSPIRATION.  i4I 

fame  cnfe?  have  even  paded  fever.il  years,  during 
the  whole  of  which  period  tlry  appeared  to  be 
almo't  emirely  -.'cprived  of  the  ufe  and  advantages 
of  refpiration. 

§  J9T- 

Finally,  It  does  not  appear  improbable,  but 
that  the  interior  f.iface  of  the  alimentary  canal, 
may  alfo,  befides  its  other  primary  functions,  be 
perpetually  engaged  in  the  performance  of  a  phlo- 
giflic  procefs,  not  unlike  that  conducted  by  the 
Jkin  and  pulmonary  fy/iem. 

This  cnnal  or  tube  appears,  indeed,  to  be  the 
only  interior  part  of  the  body,  except  the  lungs 
themfelves,  to  which  the  atmofpheric  air  has  free 
accefs ;  but  that  the  air  has  really  free  accefs  to 
the  prima  vjaa  or  firjl  pafjages,  as  they  are  called, 
and  that  we  f wallow  that  elaftic  fluid  in  con- 
fiderable  quantities,  are  matters,  much  too  plain, 
to  fland  in  need  of  any  proof. 

Further,  That  the  air  which  we  fwallow 
undergoes  a  change  very  fimilar  to  the  change 
fuffered  by  that  taken  by  infpiration  into  the 
lungs,  is  fatisfactorily  demonftrared  by  the  nature 
of  the  air  contained  in  the  whole  alimentary  canal. 

Finally, 


M2  OF  THE  SENSORIUM 

Finally,  To  all  thofe  concurring  circum(lance9 
we  may  further  add,  that  truly  aftonifhing  con- 
geries of  fmall  blood  veflels,  fpread  in  profufion 
over  the  interior  furface  of  the  inteftines,  which 
is  commonly  believed  to  be  equal  in  extent  to  the 
external  fuperficies  of  the  whole  body. 


SECT.    XV. 

OF  THE  SENSORIUM  AND  NERVES. 

§     I92. 

VV  E  come  now  to  treat  of  another 
clafs  of  the  functions  of  the  human  body,  which 
embraces  what  we  denominated  the  animal  fane- 
tions  (§  63):  by  means  of  thefe,  an  uninterrupted 
commerce  and  intercourfe  are  kept  up  between 
the  body  and  the  various  faculties  of  the  mind. 
They  belong  therefore  exclufively,  (as  indeed  the 
name  itfelf  plainly  imports,)  to  organifed  and  ani- 
mated bodies ;  but  as  they  pervade  the  whole 
animal  kingdom  more  univerfally  than  the  vital 
functions,  they  appear  to  have  an  exceedingly  ju ft 
and  well  founded  claim  to  the  epithet,  animal. 

§  J93- 


AND  NERVES-  143 

§    J93« 
The  organs  which  are  principally  fubfervient  to 

the  exercife  of  thefe  functions  are,  the  cerebrum, 
the  cerebellum,  and  their  appendage  the  medulla 
fpinalis,  together  with  the  nerves  that  originate 
from  thefe  three  fources.  The  whole  of  thc-fe 
organs  may,  with  fufficient  propriety,  be  ar- 
ranged under  two  leading  claffes,  namely,  the  Se?i- 
forium  and  Nerves.  The  former  of  thefe  em- 
braces (if  we  except  the  nerves  themfelves,  and 
thofe  parts  which  conftitute  their  more  immediate 
origins)  all  the  remainder  of  that  whole  fyftem, 
which  forms,  more  particularly,  the  vinculum  or 
medium  of  connexion,  that  exifts  between  the 
offices  or  functions  of  the  nerves  and  our  nobler 
part,  the  faculties  of  the  mind. 

§    194* 

On  this  divifion  is  founded  that  beautiful  obfer- 

vation  of  the  illuftrious  Sommering,  in  which  he 
alledges,  that  the  relative  magnitude  which  the 
two  preceding  clalfes  of  organs  bear  to  one 
another,  correfponds  fo  accurately  with  the  fa- 
culties of  the  mind,  that  the  fmaller  and  lefs  bulky 
the  nerves  of  animals  are,  when  compared  to  the 
fize  of  the  other  organs  or  parts  which  we  have 
comprehended  under  the  denomination  of  Sen- 
forium,  the  more  vigorous  and  active  are  the  fa- 
culties or  their  minds.    In  this  refpeel  he  obferves, 

that 


144  OF  THE  SEKSORIUM 

that  man  may  be  faid  to  pfcffda  the  largeft  cere- 
brum  or  brain,  it"  its  bulk  be  compared  to  the 
fmall  fize  of  the  nerves  that  originate  and  proceed 
from  ir,  but  not  if  its  weight  be  compared  with 
the  relative  weight  of  the  whole  body. 

§  x95- 
Befides  the  bony  cranium  or  fkull,  in  which  the 
cerebrum  iifelf  is  endofed,  it  is  dill  farther  inverted 
with  three  involucra  or  coverings ;  thefe  are  the 
dura  and  pia  ?uatres,  between  which  is  expanded 
the  third,  viz.  the  tunica  arachnoidea* 

§    196. 

The  dura  mater,  which  lines,  as  a  periofteum, 
the  cavity  of  the  encephalon,  is  lengthened  out 
into  a  variety  of  partitions  or  proceffes.  By  its 
falciform  procefs,  which  is  the  mod  prominent  and 
remarkable,  it  feparates  from  each  other,  the  two 
hemifpheres  of  the  brain  ;  while,  by  means  of  that 
procefs  -called  the  tentorium,  it  forms  a  partition 
between  the  cerebellum  and  the  parts  fituated  above 
it,  and  thus,  by  giving  fupport  to  the  pofterior 
lobes  of  the  brain,  prevents  them  from  making  an 
undue  preflure  on  the  fubjacent  cerebellum. 

Further,  the  dura  mater,  by  various  duplicaturcs 

or  doublings  of  its  own  membrane,  forms  what 

are  called  the  venous  finufes,  while  it  gives  them  at 

4  the 


AND  NERVES.  145 

the  fame  time  firmnefs  and  fupport,  and  prevents 
them  from  being  unduly  compreiTcd.  Through 
thefe  finufes  the  blood  of  the  encephalon,  or  parts 
contained  within  the  cranium,  glides  back  towards 
the  heart :  this  blood  is  faid,  by  phyfiologifts,  to 
poffefs  properties  peculiar  to  itfelf,  and  appears, 
from  attual  calculation,  to  be  fo  confiderable  in 
quantity  as  to  amount,  at  leaft,  to  one  tenth  part 
of  the  whole  mafs  of  blood  contained  in  the  human 
body. 

§  J97- 
Next  to  the  dura  mater  lies  the  tunica  arachnoU 
dea,  fo  called  from  its  extreme  tendernefs  and  filmy 
texture.  It  is  deftitute  of  blood-veilels,  (§  5.J, 
and  does  not,  any  more  than  the  dura  mater,  enter 
the  various  Juki  or  furrows,  and  receive  the  dif- 
ferent eminences  or  ridges,  which  mark  the  fur- 
face  of  the  cerebrum,  but  only  expands,  with  uni- 
formity, over  the  whole  volume  of  that  important 
vifcus. 

§    19S. 

Very  different  from  this  is  the  ftate  and  fitua- 
tion  of  the  internal  involucrum  or  covering  of  the 
brain,  on  which  the  ancients  bellowed  the  name 
of  pia  mater.  This  membrane  every  where  ac- 
companies the  cortical  part  of  the  cerebrum  fo 
clofely,  that  the  innumerable  fmall  blood-veffels, 

vol.  1.  K  with 


1 45  OF  THE  SENSORIUM 

with  which  it  is  profufely  fupplied,  enter,  and 
even  perforate  the  cortex  itfelf,  with  their  infini- 
tude of  minute  ramifications  ;  hence,  when  the  pia 
mater  is  feparatcd  by  force  from  the  cerebrum,  its 
external  furface  prefents  a  fmooth  and  exquifitely 
beautiful  polifh,  while  its  internal  furface,  on  the 
contrary,  is  confiderably  villous,  and  refembles,  not 
a  little,  thofe  delicate  radicles  by  which  the  moffe« 
adhere  to  their  native  foil,  or  places  of  growth. 

§  i99- 

Both  the  cerebrum  and  cerebellum  are  compof- 

ed  of  a  variety  of  parts,  different  from  each  other 
both  in  texture  and  figure,  the  ufes  of  which  have 
been  hitherto  generally  unknown  :  thefe  parts  are 
particularly  diftinguifhed  by  the  four  ventricles,  as 
they  are  called,  the  communication  between  which 
has  been  of  late  traced  and  developed,  with  the 
utmoft  accuracy,  by  the  illuftrious  Monro  :  of 
thefe  ventricles,  the  two  anterior  and  the  fourth 
conta'n  what  are  denominated  the  plexus  cboroidei, 
the  ufes  and  functions  of  which  are  alfo  involved, 
as  yet,  in  intricacy  and  doubt. 

§    2CO. 

In  all  parts,  of  both  the  cerebrum  and  cerebel- 
lum, there  exiii  two  kinds  of  fubilance,  one  of  a 
cineritious  or  alh-colour,  which  is  called  the  corti- 
cal part,  although  it  does  not  always  form  the 

exterior 


AND  NERVES.  M7 

exterior  (tratum,  the  other  white  and  mining,  and 
therefore  called  the  medullary  portion.  Agree- 
ably to  the  obfervations  of  the  illuftrious  Som- 
mering,  there  is  interpofed  between  the  two  fore- 
going fubflances,  flill  a  third,  of  a  colour  border- 
ing on  white  ;  this  body  is  moft  confpicuoufly  ob- 
fervable  in  the  arbor  vita  of  the  cerebellum,  and 
in  the  poflerior  lobes  of  the  cerebrum. 

§    201. 

The  proportion,  which  the  cineritious  fubflance 
bears  to  the  medullary,  decreafes  as  life  advances; 
^ius,  in  infants  it  is  greater,  in  adults  lefs.  Almoft 
the  whole  of  this  cineritious  fubftance,  is  com- 
pofed  of  an  immenfe  affembiage  and  contexture  of 
the  fmallefl  fized  blood-veffels,  together  with  veffels 
of  an  order  flill  inferior,  even  (o  minute  as  to  be 
incapable  of  admitting  any  thing  except  a  white 
or  colourlefs  fluid  of  the  mod  exquifite  tenuity, 
(§  79.)  :  a  fmall  number  of  thefe  veffels  paffes 
into  the  medullary  portion,  which  appears  to  con- 
tain in  its  own  compofition,  (befides  thefe  minute 
veffels  and  a  quantity  of  very  tender  cellular  mem- 
brane), a  foft  pultaceous  parenchyma,  in  which 
phyfiologifls,  even  when  armed  and  aided  by  the 
moft  powerful  glaffes,  have  not  yet  been  able  to 
difcover  any  uniform  and  definite  texture. 

K  2  §  20a. 


t48  OF  THE  SENSORIUM 

§     202. 

In  the  cerebrum  is  obfervable  a  perpetual  but 
very  gentle  motion,  bearing  fuch  a  relation  and 
exact  correfpondence  to  the  procefs  of  refpiration, 
that  while  the  lungs  are  collapfed,  and  their 
volume  diminifhed  in  the  act  of  exfpiration,  the 
cerebrum  is  flightly  elevated,  but  immediately 
fubfides  again,  when  the  thorax  is  dilated  br 
means  of  a  fubfequent  act  of  infpiration. 

§  203. 
What  has  been  called  by  phyfiologifts  the  me- 
dulla oblongata,  terminates  in  the  medulla  fpinalis, 
which  is  contained  in  that  flexible  tube,  formed 
by  the  vertebrae  of  the  fpine  or  back,  and  is  flill 
clothed  in  the  fame  membranes  which  we  have 
already  feen  inverting  the  cerebrum  or  brain  itfelf : 
further,  as  the  brain,  fo  likewife  the  fpinal  marrow, 
is  found  to  coniift  of  two  kinds  of  fubflance,  with 
this  ftriking  circumftantial  difference,  however, 
that,  in  the  latter,  the  cineriuous  or  afh-coloured 
fubftance  forms  the  internal,  whilft  the  fhining  or 
medul'ary  compofes  the  external,  part. 

§   204. 

From  each  of  the  foregoing  fources,  namely, 

the  cerebrum  and  cerebellum,  together  with  the 

medulla  fpinalis,  the  nerves  primarily  derive  their 

origins.     Thefe  are  fmall  ropes  or  cords,  of  a 

colour 


AND  NERVES.  i49 

colour  more  or  lefs  whitim,  differing  likewife  in 
their  degree  of  firmnefs),  which  are  minutely 
diflributea  throughout  almoft  all  the  other  foft 
parts  of  the  human  body.  This  opinion  of  the 
minute,  and  it?iiverfal,  diflribution  of  the  nerves 
through  every  part  of  the  human  fyftem,.  though 
admiJTible  as  a  general  rule,  is,  however,  fubjeft 
to  certain  well  founded  exceptions. 

§   204. 

For  it  appears  from  an  infinitude  of  experiments 
made  by  the  illuflrious  Haller,  and  other  able 
obfervers,  that  there  are  feveral  of  the  partes 
fimilares  (or  fimilar  parts  §  46)  of  our  bodies,  in 
which,  the  knife,  and  powerfully  armed  eye  of 
the  anatomift,  have  not  been  able  to  detect  the 
{mailed  veftige  of  nerves,  and  where  neither  fur- 
gical  obfervations  nor  live  diffe&ions,  often  re- 
peated by  the  mod  dextrous  hand,  havefucceeded 
in  difcovering  even  the  fainted  phenomena  of 
feniibility. 

In  an  enumeration  of  fuch  parts,  as  appear  to 
be  deflitute  of  fenfation  and  nerves,  we  mud  em- 
brace, befides  the  naked  cellular  membrane,  the 
epidermis,  the  reticulum  mucofum,  the  hairs,  and 
the  nails. 

K  3  We 


i5o  OF  THE  SENSORIUM 

We  include  further,  the  cartilages,  and  bones, 
with  their  perioftia  and  marrow. 

To  thefe  mufl  be  added,  the  tendons,  the  aponeu- 
roses, and  ligaments;  as  alfo  mod  of  the  broader 
and  more  extenfive  membranes,  fuch,  for  example, 
as  the  dura  mater  and  tunica  arachnoidea ;  the 
pleura,  with  the  mediaftinas  and  pericardium;  the 
peritoneum;   the  cornea,  &c. 

Under  the  fame  head  we  arrange  mod  parts  of 
the  abforbent  fyftem,  but  more  efpecially  the 
thoracic  duel. 

Finally,  This  catalogue  of  fuch  parts  as  neither 
poffefs  nerves,  nor  are  endued  with  fenfibility, 
fhall  be  clofed,  by  the  addition  of  the  fecundities, 
and  umbilical  cord. 

§   206. 

The  primary  or  nafcent  origins  of  the  nerves, 
emerging  from  the  fenforium  itfelf,  have,  as  yet, 
eluded  the  moft  zealous  researches  of  the  fubtle 
knife  and  prying  eye  of  the  anatomifl  :  it  there- 
fore flill  remains  a  matter  of  controverfy  and 
doubt,  whether  the  nerves  on  each  fide  of  the 
body  derive  their  origins  from  the  cor re/ponding, 
or  from  the  oppofite  fide  of  the  fenforium  ?  Cer- 
tain pathological  phenomena  appear  indeed  to  fa- 
vour 


AND  NERVES.  151 

vour  the  latter  of  thefe  opinions.  It  has  been  alfo 
lately  eftablifhed  by  the  illuftrious  Sommering  that 
a  true  decufTation  or  eroding  of  the  optic  nerves 
does  actually  exift. 

§  207, 
A  certain  continuation  of  the  pia  mater  accom- 
panies the  medullary  part  of  the  nerves  in  their 
courfe,  in  fuch  a  manner,  as  to  form  for  them  a 
vafcular  cortex,  or  covering,  of  extreme  tender- 
nefs.  No  fooner,  however,  do  thefe  cords  emerge 
from  the  cerebrum  >  or  the  fpinal  marrow,  than 
they  affume  a  very  fmgular  habit  and  appearance, 
by  which  they  may  be  readily  diftinguiflied  from 
almoft  all  the  other  fimilar  parts  of  the  body. 
This  peculiarity  of  appearance  is  produced  by 
fmall  plicae  or  folds,  which  they  exhibit,  running 
in  angular  directions,  more  or  lefs  oblique.  Thefe 
folds  were  formerly  defcribed  by  P.  P.  Molinel, 
who  compared  them,  not  inconfiftently  with  pro- 
priety and  fitnefs,  to  the  rugas  of  the  Iumbricus, 
or  round  worm,  or  to  the  fmall  rings  of  the  afpera 
arteria. 

§  208. 

The  nerves,  especially  thofe  of  the  fingle  or 
unpaired  orders,  fuch,  for  inftance,  as  the  inter- 
coital   and    vagantes    or   wandering    nerves,    are 
every  where  furnilhed   with  ganglia,  i.  e.  fmall 
K  4  bulbs, 


152  OF  THE  SENSORIUM 

bulbs,  of  a  texture  confidcrably  compart,  and  of 
a  cineritious  colour,  fomewhat  inclining  to  a  pale 
red  :  the  functions  and  ufes  of  thefe  bodies  in  the 
animal  economy  have  not  yet  been  fatisfaftorily 
afcertained  and  demonflrated.  We  are,  however, 
in  the  mean  time,  mod  inclined  to  adopt  the 
opinion  formerly  entertained  reflecting  thefe  fub- 
ftances  by  the  ingenious  Zinn.  That  acute  phy- 
iiologift  believed  the  ganglia  to  confift  entirely  of 
mazy  complications  and  intertextures  of  minute 
nervous  filaments  originating  from  di  Terent  fources. 
In  confequence  of  this  intricate  and  uninveftigated 
texture  of  thefe  bodies,  he  conjectured,  that  each 
nervous  filament,  or  thread  proceeding  from  them, 
participates,  or  contains  in  its  compofition,  a  part 
of  every  filament  that  enters  into  their  ftruclure, 
however  numerous  thofe  filaments  may  be,  or 
however  different  the  fources  from  which  they 
originate. 

§   209. 

Neither  does  there  appear  to  exift  any  very 
material  difference  between  the  nature  of  ganglh, 
as  jufl:  defcribed,  and  of  what  are  called  plexus 
nervqfi.  Thefe  latter  are  alfo  indebted,  for  their 
exigence  and  form,  to  a  fimilar  concurrence  and 
anaftomofin.T  intertexture  of  nerves  that  originate 
from  different  fources.  The  compofition  of  fuch 
nervous  filaments  as  ramify  and  proceed  from  thefe 

plexus 


AND  NERVES.  153 

plexus  nervoji,  appears  to  be  alfo  perfe&ly  analo- 
gous to  the  composition  of  thofe,  that  originate 
from  the  ganglia,  of  which  we  have  already 
fpoken. 

5    210. 

But  as  the  nafcent  origins  of  the  nerves,  fo  like- 
wife  (with  a  few  exceptions),  the  final  termina- 
tions of  their  extreme  ramuli,  or  remote  filamentary 
branches,  are  as  yet  involved  in  the  depth  of  ob- 
fcurity.  For  if  we  except  tfcofq  tew  n.  rves  that 
terminate  in  a  kind  of  rr.edullary  expanfion,  as  the 
optic  nerve  in  the  retina,  and  the  foft  portion  of 
the  feventh  pair,  in  that  pulpy  zone,  contained  be- 
tween the  fpiral  laminse  of  the  cochlea  of  the  ear 
— If,  I  fay,  we  except  thefe  two  nerves,  the  eva- 
nefcent  filaments  of  fuch  of  the  others  as  enter  the 
vifcera,  the  mufcles,  the  fkin,  &c.  become  fo  mi- 
nutely blended  with  the  real  parenchyma  of  the 
parts  on  which  they  are  diftributed,  and  gradually 
aflfume  fuch  a  pulpy  confidence,  that  the  eye  of 
the  anatomifl:  can  no  longer  trace  them  through 
their  mazy  courfes. 


SECT. 


154  OF  THE  NERVOUS  SYSTEM. 


SECT.     XVI. 

OF  THE  FUNCTIONS  OF  THE  NERVOUS  SYSTEM 
IN  GENERAL. 

§    211. 

WE  have  thus  fecn,  that  of  the  fen- 
forium,  and  nerves  fo  generally  and  minutely 
diflributed  throughout  moll:  parts  of  the  body,  a 
complete  fyflem  is  beautifully  conftituted,  which, 
during  the  continuance  of  life,  fcrves  as  a  medium 
of  communication  and  mutual  intercourfe  between 
the  body  and  the  mind. 

§  212. 
Various  circumftancrs  and  phenomena  combine 
in  rendering  it  probable,  that  the  mind  is  indeed 
attached  and  clofely  connected  to  the  brain  itfelf. 
That  the  brain  is  thus  honoured  and  dignified  in 
its  alliance  is  very  powerfully  and  ftrikingly 
evidenced,  by  mod  of  the  inftruments  of  fenfation 
being  fituated  in  the  very  vicinity  of  that  organ  ; 
by  the  aftoniming  conformation  of  its  various 
parts,  confidered  with  regard  to  their  figure  and 
flructurc  ;  but  more  efpeciaily  by  the  phenomena 
attendant  on  its  morbid  rufec'iions. 

S  213. 


OF  THE  NERVOUS  SYSTEM.  i5$ 

§  213. 
With  refpeft  to  that  connexion  of  which  we 
have  juft  hinted,  I  would  further  obferve,  that 
certain  phyfiologifts,  wantonly  fporting  in  the  de- 
lufive  fields  of  imagination,  have  fufFered  them- 
felves  to  be  fo  far  influenced  by  the  form  and 
fituation  of  particular  parts  of  the  encephalon, 
that  they  have  confidered,  and  even  endeavoured 
to  prove,  fometimes  one,  fometimes  another  of 
thefe  parts,  to  be  indeed  the  very  feat,  and  royal 
court,  (as  it  were)  of  the  mind.  This  honorary 
and  fublime  privilege,  of  affording  a  faered  feat 
to  our  nobler  and  immortal  part,  fome  meta- 
phyfical  phyfiologifts  have  been  folicitous  to 
beflow  on  the  pineal  gland*,  others  on  the 
cerebellum,  others  on  the  corpus  caliofum  f,  and 

*  In  favour  of  the  Cartefian  hypothecs,  fome  degree  of 
teftimony  appeared  to  be  derived  from  the  diifeftions  of 
certain  maniacs,  in  whom  the  pineal  gland  was  found  in- 
verted with  calculous  concretions.  On  more  accurate  ob- 
fervation,  however,  it  was  difcovered,  that  not  only  in 
maniacs,  but  alfo  in  numerous  other  fubjedts  poftefling  the 
moft  complete  degree  of  mental  fanity,  this  fame  glandular 
body  was  furrounded,  from  about  the  1 2th  year  of  life,  by 
minute  fandy  concretions  of  a  pearl-like  appearance. — CI. 
Sommering  de  lapillis  vel  prope  vel  intra  glandulam  pinea- 
lem  fitis,  f.  de  acernulo  cerebri  Mogunt.  1785.     8. 

f  Thofe  fictitious  prerogatives  both  of  the  cerebellum  and 
corpus  caliofum  are  refuted  in  a  very  mafterly  manner  by 

Zinn 


256  OF  THE  NERVOUS  SYSTEM. 

others,  again,  on  that  part  which  has  been  deno- 
minated pons  Varolii. 

§    214. 

We  are  not  by  any  means  to  fuppofe,  that  the 
whole  energy  of  the  nervous  fyftem  depends  on 
the  encephalon  alone  ;  it  is  alfo  derived  in  part 
from  the  fpinal  marrow,  and  even  the  nerves 
themfelvcs  pofTcfs  fuch  a  degree  of  inherent  or 
native  energy,  as  is  fufficient  of  itfelf  to  throw  the 
mufcles  into  a  ftate  of  convulfion.  This  native  or 
exclufive  energy  of  the  nerves,  appears  to  be 
principally  fnpported  and  preferved  by  that  vaf- 
cular  cortex  or  covering  of  thofe  organs,  of  which 
we  briefly  fpoke  on  a  former  occafion  (§  205). 
It  is,  however,  a  truth  which  ought  not  to  be  for- 
gotten, that  this  inherent  power  of  the  nerves 
themfelves  is  lefs,  and  that  energy,  on  the  con- 
trary, which  is  derived  immediately  from  the 
encephalon,  greater,  in  man,  than  in  other 
animals,  efpecially  fuch  as  are  fupplied  with  cold 
blood. 

§    2I5- 
The  onice  of  the  nervous  fyflem  appears,  in  a 
particuler  manner,  to  be  two-fold.  Firji,  by  means 

Zian  in  his  "  Expcrim.  circa  corpus  callofum,  cerebellum, 
duram  meningem,  in  vivis  animalibus  inftitut.  Goctting. 
3719.     4. 

of 


OF  THE  NERVOUS  SYSTEM.  15) 

of  this  fyftem,  other  parts  of  the  body,  efpecially 
fuch  mufcles  as  are  fubjected  to  the  influence  of 
the  will,  are  excited  to  motion  ;  of  this  function, 
however,  we  will  treat  more  fully  in  another 
place.  But,  fecondly,  the  nerves  are  peculiarly 
fubfervient  to  fenfation  ;  whatever  fenfible  impref- 
fions  are  made  on  the  body,  they,  like  active  he- 
ralds, convey  and  announce  immediately  to  the 
fenforium,  and  there  give  rife  to  perception. 

§  216. 
Finally,  the  fenforium  is  evidently  poffeffed  of 
the  following  very  lingular  faculty  or  power,  viz. 
that,  having  received  fenfible  impreffions  through 
the  medium  and  agency  of  certain  nerve?,  it  is 
able  to  re-act  again  in  its  turn,  not  only  on  the 
fame  nerves,  but  alfo  on  fuch  as  are  completely 
different.  In  tellimony  of  the  truth  and  authen- 
ticity of  this  pofition,  it  will  be  fufficient  to  men- 
tion the  action  of  the  retina,  when  affected  by 
light,  on  the  fenforium,  and  the  re-action  of  this 
latter,  again,  in  either  conilricting  or  dilating  the 
iris. 

§    217. 

It  is  principally  from  this  lad  fource,  fha't  we 
are  to  derive  and  explain  mo  ft  of  the  effects  of 
the  imagination,  and  paffion?  of  the  mind,  0.1 
the  human  body  :  of  tlufe  eiTcfts  we  will  fpeak 

more 


158  OF  THE  NERVOUS  SYSTEM. 

more  fully  on  a  future  occafion.  To  the  fame 
fourcc,  alfo,  mud  we  refer  that  extenfive  and 
diverfified  confent  of  the  nervous  fyftem,  which 
prevails  throughout  almoft  the  whole  body  (§  14.), 
and  the  aftonifhing  power  and  influence  of  the 
fame,  over  moft  of  the  other  functions  of  the 
animal  economy. 

§    218. 

That  the  phenomena  which  we  have  juft  men- 
tioned, proceed  from  certain  properties  effential 
to  the  nervous  fyftem,  is  a  pofition,  that  appears, 
from  obfervation  and  experiment,  to  be  founded 
on  the  mod  indubitable  evidence.  But,  to  eluci- 
date and  explain  the  manner  in  which  this  fyftem 
atts,  in  the  production  of  fuch  phenomena,  is, 
indeed,  a  difficulty  of  the  utmoft  magnitude. 

§  219. 
When  we  view  the  fubjeel:  in  a  general  light, 
the  various  opinions,  which  have  at  different  times 
been  advanced  on  this  contefled  point,  may  be  all 
referred  to  two  leading  dalles :  one  of  thefe 
alleges  the  action  of  the  nervous  fyftem,  to  de- 
pend on  a  certain  ofcillatory  motion  ;  while  the 
other  fuppofes  it  to  be  produced  by  the  motion  of 
a  peculiar  fluid,  refpecting  the  nature  of  which 
phyiiologifts,  again,  hold  different  opinions.  Thus, 
while  feme  believe  this  fluid  to  be  animal  fpirits, 

contained 


OF  THE  NERVOUS  SYSTEM.  159 

contained  in,  and  palling  through,  vefiels,  others 
contend,  that  it  is  a  certain  modification  of  matter, 
limijar  to  fire,  electricity,  or  the  magnetic  effluvia* 

§    220. 

Although  I  am  difpofed  to  adopt  neither  of 
the  above  opinions  as  my  own,  yet  it  is  proper  to 
obferve,  that  moil  of  the  arguments,  by  which  the 
advocates  of  either  hypolhefis  have  endeavoured  to 
invalidate  the  other,  appear  to  me  to  be  as  crude 
and  inconclufive,  as  they  ought  to  be  fubtle,  inge- 
nious and  forcible.  This  obfervation  applies,  as 
well  to  the  arguments  made  ufe  of  to  prove  the 
ofcillations  of  the  nerves,  as  to  thofe  advanced  for 
the  purpofe  of  efhblifhing  the  exigence  of  a  ner- 
vous fluid. 

§  221. 
If,  indeed,  our  views  of  the  fubjeft  be  not  erro- 
neous, the  two  foregoing  opinions  may,  without 
impropriety,  be  united,  and  thus  a  third  one 
formed,  more  plaufible,  at  Ieaft,  than  either  of 
the  originals,  namely,  that  a  certain  nervous  fluid 
does  actually  exiil,  and  that  this  fluid  is  a!fo  capa- 
ble of  motion,  and  of  being  thrown  into  ofcillatory 
vibrations,  when  fubjecled  to  the  action  and  influ- 
ence of  ftimuli. 

§   222. 


j6o  OF  THE  NERVOUS  SYSTEM. 

§    222. 

Not  to  mention  various  other  evidences,  which 
might  be  obvioufly  deduced,  from  the  different 
phenomena  of  the  nervous  fyftem,  the  Jiruflure  of 
the  brain  itfelf,  which  bears  a  ftriking  refemblance 
to  that  of  certain  fecreting  vifcera,  appears  indeed 
to  be  highly  in  favour  of  the  exigence  of  a  nervous 
fluid.  It  is  furely  a  matter  too  obvious  to  admit 
of  controverfy,  that  there  is  no  more  need  of  any 
direft  tubes  and  canals,  for  the  diftribution  of 
fuch  a  fluid  through  the  nerves,  than  there  is,  for 
the  conveyance  of  a  liquid  through  brown  paper, 
or  any  other  nitre. 

The  nugatory  calculations,  rendering  the  aflo- 
nifliing  rapidity,  with  which  the  animal  fpirits  have 
been  fuppofed  to  hurry  through  their  nervous 
canals,  in  all  pans  of  the  fyftem,  are  fu!j<:ets  too 
hypothetical'  and  vifionary  to  merit  our  time,  or 
command  our  attention. 

§  223. 
That  an  ofcillation  of  the  nerves  does  indeed 
exift,  is  a  pofition,  powerfully  fupported  by  a  great 
variety  of  very  ftriking  and  pointed  phyfiological 
phenomena.  This  ofcillation  mud  not,  however, 
be  fuppofed  to  bear  any  refemblance  to  the  rude 
vibrations  of  tenfe  chords,  but  is  fuch  a  fubtle, 
tremulous  motion,  as  may  be  readily  conceived  to 
2  take 


OF  THE  NERVOUS  SYSTEM.  10T 

rake  place  in  the  tender,  pulpy  fubftance  of  the 
brain.  That  hearing  is  excited  by  an  ofcillation 
of  a  liquid,  has  been  reduced  to  fatisfa&ory  de- 
monftration.  That  an  ofcillatory  motion  fomewhat 
fimilar  takes  place  alfo,  in  the  act  of  vifion,  is 
(though  we  fhouid  not  be  willing  to  repofe  impli- 
cit confidence  in  the  opinions  of  Leon.  Euler)  a 
pofition  founded,  at  lead,  on  firong  probabilities. 
That  the  action  of  the  other  fenfes  depends  alfo 
on  an  ofcillatory  motion  of  a  fimilar  nature,  is  an 
opinion,  which  was  not  only  embraced  by  the 
illuftrious  Newton*,  but  has  been  fince  ably  and 
fuccefsfully  defended  in  the  writings  of  the  fuga- 
cious Hartley.  It  is  on  the  principle  of  the  exis- 
tence of  fuch  a  motion,  that  this  laft  mentioned 
author,  has  firfh  happily  accounted  for  the  affoci- 
ation  of  ideas,  and  then,  by  the  aid  of  this,  pro- 
ceeded to  explain,  with  the  utmoft  ingenuity,  mod 
of  the  functions  performed  by  the  different  facul- 
ties of  the  mind  |. 


*  Vide  ejus  Quscftiones  ad  calcem  optices.     Qu.  23.  p. 
355.  edit.  Lond.   iynj-8. 

■f  David  Hartley's  Obfcrvations  on  man,  his  frame,  his 
duty,  and  his  expectations.     Lond.  1749,  vol.  ii.  8. 


vol.  i.  L  SEC  T. 


1 62  THE  TOUCH. 


S  E  C  T.     XVII. 


THE  EXTERNAL  SENSES  IN  GENERAL,  BUr 
PARTICULARLY  OF  THE  TOUCH. 

§    224. 

V7NE  office  of  the  nerves,  as  we  have 
already  had  occafion  ro  obferve,  confifts  in  com- 
municating to  the  Tentorium,  impreffions  made  by 
external  objects.  This  they  do  through  the  me- 
dium of  the  external  fenfes,  which  officiate  as 
watchful  centinels  to  the  body,  and  diligent  in- 
flructors  to  the  mind. 

Thefe,  therefore,  (hall  constitute,  at  prefent,  the 
folc  objeel  of  our  consideration.  For  to  arrange 
among  the  fenfes,  the  ftimulus  or  propenfity  which 
animals  feel  to  evacuate  their  firces,  the  fenfatioa 
of  hunger  to  which  they  are  fuhjected,  or  other 
internal  calls  of  nature  of  a  fimilar  kind,  would 
be,  as  Haller  formerly  obferved,  an  unnecefiary 
fpecies  of  fubtility  and  refinement. 

225. 

It  ought  to  be  remembered,  that  no  other  clafs 

of  functions  belonging  to  the  animal  economy,  is 

fubjected  to  fuch  an  aftonifhing  variety  in  different 

individuals,  as  that  of  the  external  fenfes,  which 

conflirutes 


OF  THE  TOUCH.  163 

constitutes  the  fubjec'r.  of  our  prefect  confidenuion. 
This  infinite  diveriiry,  which  exifls  between  thefe 
fenfes  in  different  individuals,  is  either  natural  or 
acquired,  and  relates  to  their  greater  or  lefs  acu- 
men or  fharpnefs,  their  fubtlety,  or  to  the  manner 
in  which  they  are  affe&ed  by  fimilar  applications 
of  the  fame  ftimuli. 

§  226. 
In  giving  an  entire  and  complete  account  of 
the  external  fmfes,  it  appears  moll  proper  to 
begin  with  the  touch,  this  being  the  one  which 
manifests  itfelf  at  the  earlieft  period  in  the  human 
fubjec'r.  after  birth.  The  organ  of  the  fenfe  of 
touch  is  expanded  over  the  whole  fuperficies  of 
the  body,  and  is  fo  conflituted  and  formed  as  to 
be  affected  by  much  the  greatefl  number  of  the 
properties  of  external  objects. 

§  227. 
For  we  are  not  only  made  fenfible  of  certain 
qualities  of  fubftances  by  means  of  the  touch 
alone,  as  of  heat,  hardnefs,  weight,  &c.  but  there 
alfo  exift  other  qualities,  fuch,  for  inftance,  as 
figure,  diflance,  &c.  of  which  we  acquire,  a  much 
more  certain  and  accurate  knowledge  by  the  aid 
of  the  touch,  though  it  mad  be  acknowledged 
that  thefe  qualities  are  at  the  fame  time  fuhject  to 
the  cognizance  of  fome  of  the  reft  of  our  fenfes. 
L  2  §  228, 


OF  THE  TOUCH. 

§  228. 
The  touch  is  lefs  liable  to  deception  than  the 
other  fenfes ;  and  is  capable  of  becoming,  by  cul- 
tivation and  attention,  fo  exquifitely  perfect  and 
refined,  as  to  be  able  to  compenfate,  in  a  certain 
degree,  for  any  deficiency  in  its  fifttr  fenfes,  more 
efpecially  in  that  of  vifion. 

§  229. 
The  organ  of  this  fenfe  is  indeed  the  fkin  in 
general,  concerning  the  fabric  and  texture  of 
which  we  fpoke  formerly  ;  but  thofe  parts  that 
are  more  immediately  fubfervient  to  the  touch, 
arc  the  papillae  of  the  corium  or  cutis  vera;  thefe 
papillae  exhibit  various  figures  in  different  parts  of 
the  body;  they  are  indeed,  for  the  mod:  part,  ver- 
rucofc,  in  other  places  they  are  fungous,  in  others 
filamentous  or  thread-like,  &c.  under  all  which  ap- 
pearances, the  extremities  of  the  cutaneous  nerves 
terminate  after  the  manner  of  fmall  pulpy  pencils. 

§  230. 
But  by  far  the  mod  important  and  difiinguifhed 
inftruments  of  the  touch  are,  in  particular,  the 
hands,  the  fkin  of  which  is  impreiTed  with  a  great 
number  of  flriking  peculiarities.  Thus,  for  ex- 
ample, the  fkin  on  the  palms  of  the  hands,  and  on 
each  ii'le  of  the  joints  of  the  fingers,  is  fr.lcated 
and  completely  deftitute  of  hair,  for  the  purpofe  of 

facilitating 


OF  THE  TOUCH.  165 

facilitating  the  folding  or  doubling  up  of  thofe 
parrs.  The  extremities  of  the  fingers,  on  their 
internal,  and  of  the  toes,  on  their  inferior,  fur- 
faces,  are  furrowed  with  flight  and  very  elegant 
grooves  running  in  directions  more  or  lefs  fpiral : 
bu  rhe  former,  on  the  exterior,  and  the  latter  on 
the  fuperior,  fides,  of  their  terminations,  are  pro- 
tected from  injury  by  nails. 

§    *3'« 

Thefe  fcutiform  nails  are  poffeffed  only  by  man, 
and  a  few  other  animals,  (belonging  to  the  clais 
mammalia),  which  are  alfo  furnifhed  with  hands, 
and  excel  in  the  acutenefs  of  their  fenfe  of  touch. 
Thefe  nails  appear  to  be  defigned  for  the  purpofe 
of  making  a  gentle  refinance  to  the  preffure  of 
the  fingers  when  examining  fubfiances,  and  thus 
aiding  their  action. 

The  nails,  though  of  a  horny  nature,  mud 
neverthelefs  be  confklered,  on  the  whole,  as  pro- 
ductions or  continuations  of  the  epidermis  :  for 
immediately  under  them  lies  the  reticulum  muco- 
fum,  which  in  ./Ethiopians  is  black  ;  and  finally, 
beneath  this  again  is  expanded  the  corium  or  true 
fkin,  which  is  firmly  attached  to  the  perioMium  of 
the  extreme  phalanx  of  the  fingers.  Alfo  thefe 
conftituent  parts  of  the  nails  are  ftriated  in  a  lon- 
gitudinal  direction.     At   their  pofterior  margins 

L  3  (which 


i66  OF  THE  TASTE. 

(which  arc  difHnguifhed  by  fmall  femilunar  fcg- 
ments,  of  a  fhinmg  or  fomewhat  brilliant  ap- 
pearance) they  arc  fecurely  fixed  in  a  groove 
formed  by  a  reflecr.:on  of  the  cutis,  from  whence 
by  a  daily,  but  very  moderate,  increafe,  they  are 
gradually  protruded  forward,  in  fuch  a  manner,  as 
to  be  completely  renovated  in  every  term  of  about 
fix  months. 


SECT.     XVIII. 


OF    THE    TASTE. 


§     232. 

1  ASTES  are  certain  impreffions  made 
on,  and  perceived  by,  the  tongue,  an  J  alfo,  in  fome 
meafure,  by  the  adjoining  cutaneous  parts  of  the  os 
internum  (/.  c.  the  infide  cf  the  mouth);  thefe  parts 
are,  in  particular,  the  medium  palati^  the  fauces, 
the  cheeks,  and  even  the  lips  themieives  ;  with 
refpect,  however,  to  the  whole  of  thefe  auxiliary 
parts,  it  in  proper  to  obferve,  that  they  have  no 
perception  of  any  tafies  except  fuch  as  are  acrid 
or  intenfely  bitter. 

§  233- 


OF  THE  TASTE.  167 

The  principal  inftrument  of  tafte  is  //v  tongue, 
an  organ  capable  of  the  utmoft  agility  in  motion, 
very  pliable,  and  exceedingly  changeable  in  poinj: 
of  form  :  it  confifts  of  a  flelliy  texture,  which  ex- 
hibits a  (hiking  appearance,  fomewhat  referoblJng 
the  texture  of  the  heart. 

§  234. 
It  is  inverted  with  involucra  or  coverings,  which 
hear  a  fimilitude  to  the  different  llrata  of  the  cutis  : 
tbefe  arc,  the  cpithelion,  which  correfponds  to  the 
cuticle,  the  reticulum  Malpighianum,  and  laftly, 
a  papillary  membrane,  that  differs  but  little  in  its 
ilruiSiure  from  the  corium  or  true  fkin. 

§  *35- 
The  principal  difference  confifts  in  this,  that 
the  epithelion,  instead  of  a  fine  cutaneous  oil,  is 
lubricated  and  moiftened  by  mucus,  which  exfudes 
from  that  imperceptible  orifice,  named  after  Mei- 
bomius,  and  alfo  from  the  reft  of  that  glandular 
expanfion,  difcovercd  by  Morgagni :  another  point 
of  difference  is,  the  conformation  of  the  papillae, 
which  are  divided  into  the  petiolated,  the  obii/ft, 
and  the  conlzal ;  of  thefe,  the  former,  being  very 
few  in  number,  are  placed  in  a  lunated  arrange- 
ment, a:  the  root  of  the  tongue,  while  the  others,, 
being  of  various  fizc^,  are  crouded  promifcuoufly 
L  4  and 


ioS  OF  THE  TASTE. 

and  without  order,  on  the  back  of  the  tongue, 
but  more  efpecially  on  its  edges  an  J  tip,  -where 
the  fenfe  of  tulle  is  moll  acute  and  exquiiite. 

§  236. 
To  thefe  papillce  pafs  the  extreme  filaments  of 
the  lingual  branch  of  the  fifth  pair  of  nerves,  by 
the  offices  and  aid  of  which  it  appears  probable, 
that  the  fenfe  of  tafte  is  proximately  generated  and 
preferved. 

For  the  ninth  pair  of  nerves,  and  alfo  that 
branch  of  the  eighth,  which  is  diftributed  through- 
out the  tongue,  appear  to  be  fubfervient  to  the 
various  motions  performed  by  that  organ  in  chew- 
ing, fu allowing,  fpeaking,  &c.  rather  than  to  its 
function  as  the  immediate  inftruraent  of  tafte, 

§  237. 
That  the  tongue  may  exercife  the  fenfe  of  tafle 
in  perfection,  it  is  fleceflary  for  it  to  be  kept  in  a 
ftate  of  complete  humidity  ;  the  fubftance  to  be 
tailed  flaonld  alfo  be  a  liquid,  and  ought  to  abound 
with  falts  in  a  ftate  of  foiution  :  for  if  either  the 
tongue  itfelf,  or  the  fubflances  applied  to  it  be 
dry,  it  may  then  indeed  examine  them  by  the 
touch,  which  it  generally  poffeiTes  in  an  exquifite 
degree,  but  cannot  with  ftri&nefs  and  propriety 
be  faid  to  tafte  them. 

When 


OF  SMELLING.  itft, 

When  the  tongue  difcharges  the  office  of 
tailing  with  mod  perfection  and  acutenefs,  the 
papillae,  fituated  on  its  apex  and  edges,  appear  to 
be  brought  into  a  ftate  of  genuine,  though  flight, 
erection. 


SECT.     XIX. 

OF     SMELLING. 

§  238. 

£)Y  means  of  the  fenfe  of  fmelling  we 
perceive  impreffions  made  by  the  odorous  effluvia 
of  ftibftances,  which  being  inhaled  in  infpiration, 
come  in  contact  with  that  part,  in  particular,  of 
the  Schneiderian  membrane,  which  inverts  each 
fide  of  the  feptum  narium,  and  lines  the  convex 
furfaces  of  the  concha. 

§  239- 
For  although  the  whole  of  the  internal  nares, 
together  with  the  adjoining  finufrs,  which  open 
into  them,  be  lined  with  a  humid  membrane, 
fimilar  in  appearance  to  the  Schneiderian,  it 
neverthclefs  appears  to  be  diverfied  in  its  nature 
in  different  places. 

That  part  of  the  membrane,  which  is  fituated 
near  the  opening  of  the  external  nares  themfelves, 

bearing 


r7©  OF  SMELLING. 

bearing  a  ftronger  refcmblance  to  the  other  part! 
of  the  real  cutis,  is  overfpread  with  febaceous  fol- 
licles, which  are  completely  mantled  in  clutters  ol 
hair.  > 

But  that  part  which  lines  the  fepium  narium, 
and  concha,  is  of  a  fungous  nature,  and  abounds 
with  fmall  muciferous  cryptae  or  cells. 

Finally,    Thofe    portions    which    invert    tl 
parictcs  of  the  frontal,  the  fphenoidal,  the  ei 
moidal,  and  the  maxillary  finufes,  are  by  far 
moil  tender  and  delicate  of  all,  and  are  complc 
cverfpread   with  an   infinitude   of  minute  bio 
vefTels,  which   conftantly  exhale  from   their  ex- 
tremities a  fubtle  dew-hke  fluid  of  an  aqueous 
nature. 

§  240. 
The  principal,  if  not,  indeed,  the  only  ufe  of 
thofe  finufes  appears,  therefore,  to  be,  to  furniih 
a  watery  liquid,  of  fuch  a  nature,  as  has  been  juft 
defcribed,  which  being  firft  conveyed  into  the 
three  paffages  or  avenues  of  the  nares,  may  be 
from  thence  communicated  to  thofe  adjacent  parts, 
which,  we  have  already  faid,  conftitute  the  imme- 
diate inflrumtnts  of  the  fenfe  of  fmelling.  By 
thus  fupplying,  with  a  due  degree  of  humidity, 
the  parts  which  proximately  form  the  olfactory 

creans. 


OF  SMELLING.  171 

organs,  thofe  finufes  contribute,  not  a  little,  to 
preferve  the  a'cutenefs  and  perfection  of  this  ia- 
terefting  fenfe. 

For  the  attainment  of  this  end,  fuch  a  wife  pro- 
vifion  is  made  by  the  very  fituation  of  thofe  feveral 
fmufes,  that  in  whatever  pofirion  the  head  be 
fu tfered  to  reft,  one  or  other  of  them  may  {till 
difcharge  and  depofi:  a  quantity  of  this  fubtle  dew, 
on  the  immediate  feat  of  the  fcnfe  of  fmelling. 

§  241. 
The  fungous  part  of  the  nafal  membrane,  of 
which  we  have  already  fpoktn,  and  which  con- 
ftitutes  the  proximate  organ  of  fmelling,  befides, 
the  immenfe  number  of  minute  blood-vefTcls  with 
which  it  is  overfpread  (and  which  are  rendered  in 
a  particular  manner  remarkable,  by  this  circum- 
itance,  that  there  are  no  other  vefiels  in  the  whole 
body  equally  liable  to  fpontaneons  hemorrhages); 
befides  thefe  fmall  blood-veffels,  I  fay,  this  part 
of  the  membrane  is  alfo  furniflied  with  nerves, 
efpecially  from  the  firft  pair,  and  alfo  from  both 
branches  of  the  fifth  pair  :  of  thefe,  the  firft  pair 
appears  to  be  of  itfelf  folely  fubfervient  to  the  fenfe 
of  fmelling  ;  while  the  others  fuppiy  the  parts,  to 
which  they  are  diftributed,  with  branches  for  the 
purpofes  of  common  fenfation^  fuch,  for  example, 
as  that  which  gives  rife  to  freezing,  &c. 

§  242. 


17-  OF  SMELLING. 

§  242. 
The  extreme  filaments  of  thi3  firft  pair  of  nerves 
are  not,  (as  is  the  cafe  in  the  organs  of  touch  and 
tafle),  lengthened  out  and  rounded  into  papillary 
elongations,  but  appear  to  deliquate,  or  melt  down, 
as  it  were,  into  the  fpongy  and  uniform  paren- 
chyma of  the  membrane  in  which  they  terminate. 

§   243- 
In  new-born  infants,  the  chamber  deftined  for 
the  immediate  recep-ion  of  odours  is  narrow, 
as  yet  extremely  imperfect.    The  finufes,  of  which 
we  have  already  fpoken,  have  at  this  tim:  fiercely 
made  their  appearance  :  hence,  infant    do  ti  t  ac- 
quire the  fenfe  of  fmelling  till  a  late  period,  ; 
expanfion  and  complete  formation  of  their  internal 
nares  are  but  gradually  and  very  ilowly  accom- 
pllfhed.     The   larger  thofe   inflruments  become, 
and   the   more   accurately  they  ate   formed  and 
finifhed,  the  more  exquifite  will  be  the  acutenefs 
and  perfection  of  this  fenfe. 

§  244. 
Finally,  it  is  a  truth  well  worthy  of  being  re- 
membered, that  there  is  fcarcely  another  external 
fenfe,  which  pofTirfies  fuch  a  powerful  connection 
with,  and  influence  over,  both  the  fenforium  itfelf, 
and  the  internal  fenfes,  as  that  of  fmelling. 

There 


OF  HEARING.  173 

There  is  none  fubjett  to  fuch  (hiking  diofyn- 
crafies ;  none  better  calculated  either  to  produce, 
to  prevent,  or  to  remove,  paroxyfms  of  fainting. 

Neither  is  there  any  one  fufceptible  of  more 
delicate  and  pleafing  i  m  predion  s  ;  the  fmell  is, 
th  fore,  h;  !Ut  termed  by  Roufleau  the  fenfc 
of  the  imagination. 

Nor  are  there,  laftly,  any  other  fpecies  of  fen- 
fations  that  appear  to  excite  fo  clear  and  vivid  a 
remembrance,  as  that  which  fpecific  odours  recal 
to  the  memory. 


SECT.    XX. 

OF    HEARING. 
§    244. 

iOOUND,  which  is  excited  by  a  tremu- 
lous collifion  of  elaftic  fubftances,  and  propagated 
from  fonorous  bodies,  through  the  medium  of  the 
air,  is  at  length  perceived  by  the  fenfe  of  hearing, 
after  having  proceeded  onward  in  the  following 
order:  viz.  it  is  firft  received  by  a  (hell-formed 
cartilage  denominated  the  external  ear,  over  which 

a  few 


174  OF  HEARING. 

a  few  of  the  human  fpecies  pnfTefs  a  power  of 
voluntary  motion:  bun.;  colled  a  d  concen- 
trated, as  it  were,  by  means  of  this  co  icha  <  r  ,.  , 
it  pafTes  immediately  into  the  meatus  audit  onus, 
which  is  thoroughly  anointed  and  d  ftnde  1  by  a 
very  bitter  and  fomewhat  yellowifti  cerumen,  or 
wax-like  fubftance  :  at  the  internal  extremity  of 
this  meatus  auditorius  it  ftrikes  aga;nft  the  mem- 
brana  tympani,  which  is  fituat::d  in  an  oMi'jue 
pofition,  is  firmly  attached  to  an  annular  groove 
in  the  os  temporis,  and  forms  a  complete  par  ; 
between  this  meatus  auditorius,  or  pafTage  for 
found,  and  the  middle  portion  of  the  ear. 

S    246. 
Behind  this  membrane,  the  middle  portion  of 
the  ear,  denominated  the  cavity  of  the  tympanum, 
is  fo  fituated   as    to  have  its  fundus    or  bottom 
pointing  upwards  and  inwards. 

It  contains  three  fmall  bones,  belonging  to  the 
organ  of  hearing,  the  external  of  which,  called 
the  malleus,  is  connected  by  its  handle  to  the  mem- 
brane of  the  tympanum  ;  from  its  fpinous  procefs, 
which  runs  in  a  forward  direction,  a  bulb  or  globe 
is  formed,  (efpecially  in  an  adult  fubject),  with  an 
annular  groove  fnnounding  its  bafe  j  this  finall 
globular  head  refts  on  the  body  of  the  incus. 

The 


OF  HEARING.  173 

The  incus  itfelf  is  attached  to  the  minute  knob 
or  head  of  the  Jlapes,  by  its  longer  procefs,  which 
extends  nearly  to  the  middle  of  the  cavity  of  the 
tympanum. 

Finally,  the  Jlapes,  refting  its  bafis  on  the  fenef- 
tra  oralis,  looks  towards  the  vejlibulum  of  the 
labyrinth,  into  which,  found,  having  percuftuted 
agairift  the  membrane  of  the  tympanum,  is  propa- 
gated by  means  of  the  connections  of  thofe  three 
oficcula  or  final!  bones. 

S  247- 
The  Eufbchean  tube,  running  from  the  interior 

parts  of  the  fauces,  opens  alfo  into  the  cavity  of 

the  tympanum  ;  the  inferior  winding  paffage  of 

the  cochlea  enters  likewife  into  the  fame  cavity \ 

over  the  mouth  or  orifice  of  this  paffage,  called 

the  fenejira  rotunda,  a  fine  membrane  of  a  peculiar 

nature  is  expanded.     Phyfiologifts  have  not  yet 

afcertained  and  demonflrated,  in  a  clear  and  fatif- 

factory  manner,  the  ufes  of  either  of  thofe  two  lad 

mentioned  parts. 

§  248. 

Laftly,  in  the  deep  and  hidden  receffes  of  the 
$s  petrofum  lies  the  labyrinth,  or  internal  portion  of 
the  ear,  which  embraces  again  three  fevcral  parts. 

Thefc 


176  OF  HEARING. 

Thefe  arc  the  veftibuhim,  which  is  fituated  in 
the  middle  between  rhe  other  two,  and  into  which 
open,  befidcrs  the  feneftra  ovalis,  both  the  five 
mouths  of  the  femicircular  canals  that  run  in  a 
backward  direction,  and  alfo  the  fuperior  winding 
paffage  of  the  cochlea,  which  extends  and  lies 
anteriorly. 

§  249- 
The  labyrinth  itfelf  contains  a  very  fubtle,  lim- 
pid water,  which  has  been  named  after  the  illuf. 
trious  Cotunnius,  and  which  that  celebrated  phy- 
fiologiil  difcovered  to  be  abforbed  by  two  very 
minute  canals  :  thefe  fmall  canals,  called  by  Co- 
tunnius, aqueducts,  (and  by  Meckel  diverticula), 
arife,  the  one  from  the  veftibulum  itfelf,  the  other 
from  the  inferior  winding  paffage  of  the  cochlea. 

§  250. 
The  foft  portion  of  the  feventh  pair  of  nerves, 
together  with  the  hard,  (which  afterwards  paffes 
through  the  aquedud  of  Fallopius),  having  en- 
tered the  internal  chamber  of  hearing,  tranfmits 
its  medullary  filaments  through  the  perforated 
bottom  of  that  cavity.  Thefe  filaments  pafs,  in 
part,  to  the  vcftibulum  and  femicircular  canals, 
but  are  diftributed  more  efpecially  over  the  bafe 
of  the  cochlea,  where  their  extremities  are  ar- 
ranged in  fuch  a  manner  as  to  run  between  the 
2  laminas 


OF  HEARING.  17? 

laminae  or  plates  of  the  feptum  of  the  cochlea, 
exhibiting  the  appearance  of  a  fine  medullary- 
zone,  beautifully  ornamented  with  plexiform  ftria? 
or  ftreaks. 

§  251. 
The  ofcillatory  tremor  which  we  formerly  traced 
and  followed  up,  even  to  the  feneflra  ovalis, 
(§  246.),  is  from  thence  propagated  to  the  vefli- 
bulum,  where,  finally,  through  the  medium  of  the 
fubtle  aqueous  liquid  already  defcribed  (§  249.), 
it  ftrikes  and  imprefles  the  auditory  nerves  them- 
felves,  which  are  distributed  with  infinite  art  and 
ingenuity  throughout  the  mazy  circumvolutions 
of  the  labyrinth. 

§    252. 

The  impetus  of  found,  finking  againft  the  mem- 
brane, and  being  propagated  through  the  cavity 
of  the  tympanum,  is  thought  to  be  modified  and 
regulated,  not  only  by  the  mufcles  of  the  malleus 
zndjiapes,  which  appear,  in  their  contraction  and 
relaxation  to  be  fubjeft  to  the  influence  of  the 
will,  but  alfo  by  the  chorda  tympani,  which  is 
fituated  in  the  middle,  between  the  handle  of  the 
malleus  and  the  longer  leg  of  the  incus. 

tol.  1.  M  SECT. 


•178  OF  VISION". 

SECT.    XXI. 

OF    VISION. 

J-  HOSE  rolling  or  vcrfatilc  globes, 
denominated  eyes,  are  to  be  considered  as  the  im- 
mediate inftruments  of  the  fublime  fenfe  of  vijion. 
They  are  fixed  as  if  on  footflalks,  by  their  optic 
nerves  (rtfpecYmg  the  decuflation  of  which  we 
have  already  fpoken,  §  205.),  in  fuch  a  manner, 
that  their  infertions  are  not  directly  oppofite  to 
the  centres  of  the  cornea  and  iris,  but  are  placed 
behind  the  imaginary  axes  of  the  eyes,  in  fnua- 
tions  fomewhat  nearer  to  the  nofe. 

§  254. 
Each  orb  is  compofed  of  various  tun'cs  or  coats, 
which  inclofe  humours  of  different  denfities,  and 
fo  extremely  pellucid,  that  the  rays  of  light, 
having  entered  the  pupil  or  window  in  the  ante- 
rior fegment  of  the  orb,  can  pafs  through,  with- 
out the  lead  interruption,  to  its  bottom  or  oppofite 
fide. 

§   155- 
The  external  involucrum  of  the  globe  of  the  eye 
is  called  fclerotica,  the  anterior  hiatus  or  chafm  ot 

which 


OF  VISION.  i79 

which  is  clofed  up  by  the  tranfparent  cornea, 
which  is  a  lameilated  membrane,  more  or  lefs 
convex,  and  projects  in  a  flight  degree  forward, 
like  a  fegment  of  a  fmaller  globe  protruding  out 
©f  a  larger. 

§  IS6' 
Next  to  the  fclerotica  lies  the  tunica  choroidea, 
which  abounds  in  blood-veiTels,  more  efpecially 
in  verticofe  or  circuitous  veins:  this  coat  is  ftained 
on  each  fide  by  a  black  pigment,  which  loofely 
adheres  to  its  concave  furface  after  the  manner, 
and  with  the  appearance,  of  mucus. 

§   257' 
The   choroides    enclofes,   finally,    the    retina, 

which  is  the  moft  internal  of  the  common  tunics 
embracing  the  vifual  orb.  This  coat  confifts  en- 
tirely of  the  medullary  fubftance  of  the  optic 
nerve,  which  having  perforated  the  fclerotica  and 
and  choroidea,  is  expanded  on  the  concave  fur- 
face  of  this  lad  involucrum,  and  there  arranged 
with  the  utmoft  beauty  and  elegance  of  ftru&ure. 

§  258. 

The  anterior  border  of  the  tunica  choroidea 
terminates  in  a  cellular  ring,  which  is  denominated 
orbiculus  ci/iaris,  and  by  means  of  which  the  cho- 
roides is  more  firmly  attached  to  a  correfponding 
M  2  groove 


i8o  OF  VISION. 

groove  or  depreffion  in  the  fclerotica.  From  this 
cellular  girdle  or  attachment,  two  other  membranes 
of  different  kinds,  (namely,  the  iris  and  ciliary 
procejfts),  originate  and  diverge  from  each  other, 
like  two  expanded  circles. 

§  259. 
The  iris  (the  pofterior  furface  of  which,  being 
overfpread  with  a  dark  pigment,  is  denominated 
uvea)  is  fituated  anteriorly,  is  gently  convex  on 
the  furface  next  the  cornea,  and  is  furrounded  on 
all  fides  by  a  humour  of  an  aqueous  nature.  That 
fegment  of  the  iris,  which  lies  next  the  nofe  is 
narrower,  while  that  which  looks  towards  the 
temples  is  poffeffed  of  greater  expanfion.  Its  tex- 
ture confifts  entirely  of  condenfed  cellular  mem- 
brane, without  the  fmallefl:  veftige  of  mufcular 
fibres ;  upon  the  whole,  it  appears  to  be  in  reality 
a  membrane  fid  generis,  as  was  formerly  well 
obferved  by  Zinn,  and  not  by  any  means  an  ap- 
pendage to  the  choroides.  On  its  anterior  furface 
it  is  differently  coloured  in  different  individuals, 
and  while  diftended  and  animated  with  a  plenitude 
of  life,  it  exhibits  fomewhat  of  a  floccofe  ap- 
pearance. 

§   260. 

The  blood-veffels  of  the  iris  run  principally  oa 
its  anterior  furface,  and,  in  the  fcetus,  arc  con- 
tinued 


OF  VISION.  i»i 

tinued  into  what  is  called  the  membrana  pupillaris  : 
refpe&ing  the  nature  and  ufe  of  this  membrane,  [ 
have  fpoken  more  fully  in  another  place  *.  It 
appears  to  be  intended  for  the  purpofe  of  pre- 
ferving  the  iris,  (during  the  rapid  growth  of  the 
ball  of  the  eye),  in  a  ftate  of  expanfion,  and  thus 
rendering  it  more  fit  for  future  motion. 

About  the  fevcnth  or  eighth  month  of  preg- 
nancy, when  the  ball  of  the  eye  has  now  acquired 
a  confiderable  magnitude,  this  membrane  begins 
to  open  and  give  way  in  its  centre;  the  elliptical 
arches  of  its  veffels  are  retra&ed  in  a  very  gradual 
manner,  and  thus  form,  in  my  opinion,  the  J hall 
interior  ring  of  the  iris ;  it  is,  at  lead,  certain,  that 
not  a  lingle  trait  of  this  ring  can  be  difcovered  in 
the  eyes  of  a  foetus  previouily  to  the  above-men- 
tioned period. 

§   261. 

Thepojlerior  of  thofe  two  orbicular  membranes, 
of  which  we  have  already  fpoken,  (§  258)  is 
called  the  ciliary  body  or  band;  it  runs  in  a  back- 
ward direction,  and  therefore,  in  its  progrefs, 
diverges  ftill  farther  from  the  iris;  by  its  external 
border,  which  is  grofs  and  firm,  it  is  attached  to 
"'■khe.  orbiculis  ciliaris  (§  258),  but  by  its  internal, 

*  Commentat.  fociet.  fcient.  Goettingens.  T.  VII. 

M  3  which 


1 82  OF  VISION. 

which  is  more  fine  and  delicate,  it  embraces  the 
margin  of  the  capfule  of  the  lens:  it  is  alfo  (haded 
with  that  fame  dufky  pigment,  of  which  we  have 
twice  already  fpokcn. 

Its  anterior  furface,  lying  oppofed  to  the  uvea, 
is  fomewhat  flriated. 

Its  pofterior  furface,  reding  on  the  vitreous 
fubllance,  is  diftinguifhed  by  about  feventy  plicae 
or  folds,  which  exhibit  an  extremely  elegant 
fioccofe  appearance;  thefe  are  called  ciliary  pro- 
ceffes,  and  are  remarkable  for  a  vafcular  apparatus 
of  inexpreilible  fubtlety  and  beauty. 

§  262. 
In  the  eye-ball  itfelf,  the  membranes  of  which 
we  have  been  hitherto  defcribing,  there  are  en- 
clofed,  in  particular,  three  different  humours. 

The  vitreous  humour  occupies  and  fills  the 
pofterior,  and  by  far,  the  greateft,  portion  of  the 
vifual  orb.  It  is  diftributed,  in  a  countlefs  number 
of  minute  drops,  throughout  as  many  minute  cells 
of  the  membrana  hyaloidea,  in  fuch  a  manner,  that 
the  whole  mafs,  confiding,  in  part,  of  membrane, 
and  in  part,  of  lymph,  exhibits  the  appearance  of 
a  peculiar,  tremulous  jelly. 

§   263. 


OF  VISION.  x«3 

263. 
The  anterior  part  of  this  vitreous  fubftance, 
has  appended  to  hfelf,  and  embraces,  in  the  ciliary 
girdle,  a  capfule,  in  which  is  contained  the  chryf- 
taline  lens,  furrounded  on  all  fides  by  a  very 
fubtie  water,  firft  difcovered  and  defcribed  by 
Morgagni. 

This  lens  itfelf,  is  alfo  compofcd  of  extremely 
pellucid  cellular  membrane;  it  is  by  far  more 
denfe  than  the  vitreous  fubftance,  and  is  furniflied 
with  fo  minute  a  quantity  of  genuine  humour, 
that,  when  prefTed  between  the  fingers,  it  refembles 
glue  of  the  mod  tenacious  confidence,  but  at  the 
fame  time  of  aftoniihing  tranfparency. 

§  264. 
The  remaining  portion  of  the  internal  cavity  of 
the  eye,  is  filled  up  by  an  exceedingly  limpid 
aqueous  humour,  and,  by  the  expanded  orbicular 
curtain  of  the  iris,  is  divided  into  two  chambers : 
thefe  are,  the  anterior,  or  more  capacious  cham- 
ber, which  feparates  the  cornea  from  the  iris,  and 
the  pofterior  one,  of  finaller  dimenfions,  extending 
from  the  uvea  to  the  corpus  ciliare, 

§    265. 
Thefe  moil  precious  and  ineftimable  parts  of 
the  body,  as  Pliny,  the  elder,  has  emphatically 
M  4  called 


1 84  OF7.  VISION. 

called  the  eyes,  arc  fccurely  protected  from  ex- 
ternal injuries,  as  well  by  their  reclufe  fnuations 
in  their  orbits,  as  by  their  valviform  coverings, 
the  palpebral. 

Between  the  folds  of  the  palpebral  arc  planted, 
in  inmenfe  profufion,  the  crouded  febaceous  fol- 
licles of  Meibomius;  their  extreme  or  lower  edges, 
ed  with  three  or  four  phalanges  of  cilia  or 
lames,  are  kept  in  an  expanded  ftate  by  certain 
cartilages  call  d  tarft,  which  are  alfo  of  further 
fervice  in  facilitating  the  motion  of  the  palpebral 
on  the  eye-balls. 

But  (to  adopt  the  language  of  the  eloquent 
Cicero)  the  parts  fituated  immediately  above  the 
palbebrae,  being  clofely  mantled  in  the  fupercilia 
or  eye-brows  intercept  and  turn  afide  the  fweat 
flowing  down  in  ftreamlets  from  the  he..d  and  face, 
and  alfo  ferve  to  moderate,  in  a  certain  degree, 
the  exceffive  effulgence  of  light. 

§  266. 
For  the  purpofes  of  lubricating  the  eyes,  of 
preferving  their  fplendor,  and  of  wafhing  out  he- 
terogeneous fubltances,  the  tears  are  provided  : 
the  principal  fource  of  this  fluid  is  a  fmall  conglo- 
merate gland,  deeply  fituated  in  a  depreflion  to- 
wards the  external  part  of  the  circumference  of 

the 


OF  VISION.  185 

the  orbit.  The  excrerory  duels  belonging  to  this 
gland  are  numerous,  but  extremely  tender  ;  they 
are  fuppofed  to  convey,  from  both  eyes,  in  the 
courfe  of  twenty-four  hours,  about  two  ounces  of 
tears  ;  After  having  been  excreted,  the  tears  are 
again  abforbed  by  the  puncla  lacrymalia,  from 
whence  they  are  conducted  through  what  are 
called  the  comua  limacum,  or  /nail's  boms,  to  the 
lachrymal  fac,  and  from  thence  finally  difcharged 
into  the  lowermofl:  pafTage  of  the  nares. 

§   267. 

Thus  much  it  was  neceffary  to  premife  refpeft- 
ing  the  admirable  ftructure  of  the  vifual  organ. 
We  come  now  to  treat  of  the  functions  of  this 
organ,  or,  in  other  words,  to  confider  the  dadrine 
of  vifion. 

All  the  rays  of  light  which  fall  on  the  convex 
furface  of  the  cornea  pafs  through  it,  provided 
their  angle  of  incidence  be  leis  than  that  of  48 
degrees.  In  confequence,  not  only  of  the  den- 
fity,  but  alfo  the  figure  of  the  aqueous  humour, 
the  rays  are  refracted  in  that  medium>  and  turned 
a  little  nearer  to  the  real  axis. 

As  many  of  the  rays  as,  having  paffed  through 
the  pupil,  enter  the  cryftalline  lens,  mufl  necef- 

farily 


iS6  OF  VISION. 

farily,  in  this  more  denfe  medium,  be  fubjecVed 
to  a  ftill  higher  degree  of  refraction. 

But  by  means  of  the  more  attenuated  and  lefs 
refractive  vitreous  medium,  wife  provifion  is  made 
to  prevent  thefe  rays  from  uniting  in  a  focal  point 
at  too  fhort  a  diftance  :  this  point,  being  thus 
farther  removed  from  the  convex  furface  of  the 
cornea,  falls  on  the  retina,  and  there  exhibits,  in 
an  inverted  pofition,  the  images  of  a!l  objects 
prefented,  and  that  in  perfect  correfpondtnee  to 
the  nature  of  furrounding  and  attendant  circum- 
ftances. 

§  268. 
This  difference  in  the  denfity  of  the  refracting 
media  of  the  eye,  exhibits  a  very  ftriking  inflance 
of  the  exquifite  and  inimitable  workmai  ihip  of  the 
divine  creator.  By  means  of  this  diverfity,  fuch 
a  complete  remedy  is  provided  againft  the  two- 
fold feparation  or  divergency  of  the  rays  of  light, 
(the  one  arifing  from  the  different  refrangibility 
of  the  different  coloured  rays,  the  other  from  the 
very  figure  of  the  lenfesj,  that  they  are  all  finally 
collected  and  united  in  the  fame  focal  point. 

§   269. 
The  celebrated  problem,  in  which  the  caufe  is 
demanded,  wherefore  we  fee  thefe  objects  erect, 

the 


OF  VISION.  i87 

the  images  of  which  are  neverthelefs  exhibited  in 
an  inverted  pofition  on  the  retina  ?  appears  to 
admit  of  an  eafy  folution,  when  we  confider,  that 
objects  are  faid  to  be  inverted,  only  from  the 
relation  they  bear  to  others,  which  are  exhibited 
in  an  erect  pofition. 

In  as  much  then  as  the  images,  not  of  a  few, 
but  of  all  objects,  even  of  our  own  bodies,  are 
received  by  the  retina  in  the  fame  relative  pofition, 
the  fituations  and  relations  of  the  whole  of  them 
harmonize  and  correfpond  to  one  another,  equally 
as  well,  as  they  could  poffibly  have  done,  had 
their  pofitions  been  truly  erect :  in  coniequence 
of  this,  the  mind,  (which  does  not  attend  to  the 
image  itfelf,  but  to  the  fenfation  excited  by  its 
impreflion),  is  fufficiently  guarded  againff  embar- 
rafTment  and  miftake. 

§   270. 

4 
In  as  much  as  the  conditions,  efTentially  neccf- 

fary  for  the  purpofes  of  acute  and  diftinct  vifion, 

are  extremely  numerous  and  varied,  the  creator  of 

man  has  made  the  wifeft  provifion  for  thefe,  by 

endowing  the  part,    fubfervient  to  this   fublime 

fenfe,  with  a  great  variety  of  functions. 

As  a  certain  adequate,  but  yet  definite,  quantity, 
and  not  too  potent  a  glare,  of  light,  is  efTemial 

to 


i88  OF  VISION". 

to  the  exiftence  of  clear  and  perfect  vifion,  a  two- 
fold caution  is  thus  taken  ;  firft,  to  admit,  (ac- 
cording as  the  light  is  flronger  or  weaker),  a 
greater  or  lcfs  column  of  rays  to  fall  on  the  lens ; 
and  fecondly,  that  all  fuperfluous  rays  which  enter 
the  eye,  and  tend  only  to  dazzle  by  the  intenfity 
of  their  fplendour,  be  abforbed  and  rendered 
inactive. 

The  former  of  thefe  purpofes  is  effectually  ac- 
eomplifhed  by  the  motion  of  the  iris  j  the  latter, 
by  means  of  the  black  pigment. 

§     2-JU 

The  iris  poffeffes  an  aftonifhing  mobility,  by 
which  it  accommodates  itfelf  fo  perfectly  to  the 
quantity  of  tight  acting  on  it,  that  when  expofed 
to  a  more  intenfe  glare,  it  is  immediately  expanded, 
and  thus  diminifhes  the  fize  of  the  pupil,  but  when 
fubjected  to  the  action  of  a  weaker  light,  it  is 
again  retracted,  and  the  pupil  confequently  en- 
larged. 

Phyfiologifts  have  attempted  a  fatisfactory  ex- 
planation of  this  motion,  in  a  variety  of  modes, 
founded  on  different  principles ;  by  fome  it  has 
been  derived  from  diverfified  impulfes  of  the  blood 
on  the  tender  veffels  of  the  moving  part,  while 
others  have  figured  to  themfelves  the  exiftence  of 

certain 


OF  VISION.  189 

eertain  imaginary  mufcles  in  the  irh,  and  have 
committed  to  them  the  whole  of  the  phenomenon 
in  quellion,  Sec.  But  I  have  lately  made  it  appear 
in  a  feparate  paper,  that  neither  cf  thefe  modes 
of  explanation  is  well  founded,  but  that  it  is  much 
more  agreeable  to  evidence,  and  correfpondent  to 
the  phenomena  of  nature,  to  derive  the  immediate 
caufe  of  the  motion  of  the  iris  from  its  vita  pro- 
pria, or  fpecijic  life.  (§  47.)  The  more  remote 
caufe  of  this  motion,  as  we  obferved  on  a  former 
occafion  (§  256),  cannot  be  referred  to  any  other 
fource,  than  the  re-action  of  the  fenforium  itfelf. 

§  272. 
The  function  of  this  dufky  pigment,  of  which 
we  have  already  fo  repeatedly  fpoken  (§  256, 
259,  261,)  to  wit,  that  it  is  deflined  to  abforb 
the  fuperfluous  rays  of  light,  and  is  hence  of  the 
utmofl  importance  in  the  bufmefs  of  perfect  vifion, 
may,  befides  other  arguments,  be  fafely  inferred 
from  directions  of  the  eyes  of  various  animals; 
but  is  more  completely  demonftrated  and  eflab- 
limed,  by  the  morbid  conftitution  of  the  white 
-/Ethiopians,  or  Albinos,  as  they  are  called,  in 
whom,  from  a  deficiency  of  this  pigment,  the 
organs  of  vifion  are  painfully  tender,  and  the  im- 
pulfe  of  light  confequently  too  powerful  to  be 
borne. 

§  *73- 


15?®  OF  VISION. 

S  173- 
It  is  further  requifite,  that  the  focus  of  re- 
fracted rays  be  perfectly  formed  on  the  retina,  fo 
that  it  may  ftrike  the  very  point  of  vifion,  and  be 
neither  fo  far  extended  as  to  fall  behind  it,  nor  fo 
much  contracted  as  to  terminate  before  it,  in  the 
vitreous  fubftance. 

The  latter  of  thefe  deviations  from  perfect 
vifion  is  what  takes  place  in  thofe  individuals 
called  ?nyopes9  in  whom  the  lucid  cornea  is  rather 
too  convex  and  gibbous. 

But  the  former  deviation  is  that  under  which 
the  prejbyta  labour,  as  the  conformation  of  the 
anterior  parts  of  the  eyes  is  directly  the  reverfe. 

§  274- 
But  as  an  eye  perfectly  found  is  able  to  difcern, 
with  equal  diitinctnefs,  bodies,  whether  at  a 
greater  or  lefs  diflance,  it  muft,  without  doubt, 
be  furnifhed  with  peculiar  faculties  or  powers  of 
accommodating  itfelf  to  the  various  diftances  of 
objects.  That  thefe  internal  and  accommodating 
changes  of  the  eye,  are  in  a  great  meafure  pro- 
duced by  the  preffure  of  the  retti  mufcles  on  the 
ball  which  they  embrace,  is  a  pofition  fo  clear, 
and  apparently  well  founded,  as  fcarcely  to  admit 
of  a  doubt.    Befides  other  arguments  which  might 

be 


OF  VISION.  191 

be  advanced  in  favour  of  this  opinion,  I  am 
induced  to  adopt  it  in  confideration  of  the  very 
lingular  ftructure,  and  extreme  flexility,  of  the 
fclerotka,  in  the  eye  of  the  Greenland  phoca,  or 
fea-calf.  By  this  peculiarity  of  fabrication  and 
arrangement,  nature  has  made  the  moll  exquifite 
provifion  to  enable  this  amphibious  animal  to 
enjoy  at  all  times,  the  advantages  of  vifion, 
though  palling  its  life  alternately  in  media  of  very 
different  denfities. 

§  275- 
By  means  of  thefe  fame  mufcle?,  our  eye?, 
whilft  we  are  awake,  are  perpetually  agitated, 
although  with  an  almoft  infenfible  motion,  and  fo 
directed  as  to  have  their  vifual  axes  arranged  in- 
right  lines  with  the  objects  viewed.  For  although 
the  whole  of  the  retina  be  porTefTed  of  fenfibility, 
yet  it  is  not  in  every  part  equally  well  adapted  to 
receive  the  images  of  objects. 

For  at  the  genuine  axis  of  the  eye-ball,  in  the 
place,  for  example,  where  the  optic  nerve  enters, 
it  appears,  from  the  well-known  and  celebrated 
experiment  of  Mariotte,  that  the  human  eye  is 
deflitute  of  the  power  of  vifion. 

But  the  principal  focus  of  the  retina,   and  that 

which  ought  to  be  confidered  as  the  leading  and 

4  immediate 


i92  OF  VISION. 

immediate  inftrument  of  diftincl  vifion,  is  fituateci 
in  an  imaginary  axis  of  the  eye-ball,  which  is  fup- 
pofed  to  pafs  through  the  centre  of  the  cornea, 
and  to  be  thus  continued  through  the  centre  of 
the  whole  orb.  It  is  not,  however,  (as  was  lately 
obferved  by  the  celebrated  Kaeftner  in  his  com- 
ments on  certain  works  of  Boerhaave),  to  be 
from  hence  underftood,  that  we  are  unable  to  fee 
clearly  and  diftin&ly,  more  than  one  fingle  point 
of  an  object  while  the  eye  remains  perfectly  at 
reft,  and  that  we  are  obliged  to  fhift  or  alter  its 
axis  in  order  to  diftinguiih  any  other  point.  The 
cafe  is  quite  otherwife,  becaufe  the  fenfation  pro- 
duced by  one  entire  object,  is  alfo  itfelf,  like  its 
original,  or  exciting  caufe,  one  and  entire. 

§   276. 

The  habit  of  directing  the  axis  of  the  eye  with 
difpatch  and  facility  towards  the  object  of  vifion, 
is  finally  acquired  only  by  ufe  and  daily  exercife. 
That  this  is  a  pofition  founded  in  truth,  isdemon- 
ftrated  not  only  by  the  example  of  fuch  individuals 
as,  having  been  born  blind,  acquired  afterwards 
the  power  of  vifion  in  adult  age,  but  alfo  by  that 
of  tender  infants,  who  feldom  attain  to  this  happy 
facility  of  moving  their  eyes  previoufly  to  the 
third  month  after  birth. 

2  §  277. 


OF  VISION.  193 

§  277. 
To  the  fame  power  of  cudom  and  habit,  mud 
we  alfo  attribute  the  remarkable  circumdance  of 
our  feeing  objects  only  fingle,  though  our  eyes  be 
two  in  number.  New-born  infants  appear  to  fee 
objects  double,  and  double  vifion,  which  fre- 
quently continues  fometime  after  certain  difeafes 
of  the  eyes,  may  be  at  length  overcome  and  re- 
moved by  ufe  and  exercife. 

§   278. 
The  joint  power  cf  both  eyes,  with  regard  to 
the   acumen    and    ftrength   of  vifion,    does    not, 
according  to  the  calculation  of  Jurin,  exceed  that 
of  one  eye,  more  than  a  thirteenth  part. 

And,  agreeably  to  an  obfervation,  long  fince 
made  by  that  celebrated  painter  Leon,  da  Vinci, 
it  is  much  bed  in  judging  of  the  didances  of 
objects  to  make  ufe  of  one  eye  only. 

§  279- 

Finally,  In  treating  of  the  ftrength  and  per- 
fection of  the  eye,  our  former  illudrious  country- 
man, Tob.  Mayer,  demondrated,  by  a  feries  of 
very  elegant  and  ingenious  experiments,  that  the 
angle  of  vifion  ought  to  exceed,  in  dimenfions,  at 
leaft  34  feconds  of  a  degree.  From  hence  he  at 
the  fame  time  illuftrated  and  proved  the  extreme 

vol.  I.  N  perfection 


1 94  OF  VISION. 

perfection  of  the  human  eye,  becaufe  this  extent 
of  the  angle  of  vifion  may  continue  nearly  the 
fame,  under  any  light  whatever,  whether  that  of 
the  meridian  fun,  or  that  of  a  weak  lamp,  fo  that 
though  the  window  or  pupil  of  the  eye  be  greatly 
contracted  and  diminiflied,  yet  the  clearnefs  of 
vifion  can,  from  that  fource,  be  fcarcely  in  any 
degree  affected. 

§    280. 

From  hence  we  may  infer,  the  inconceivable 
fmallnefs  of  the  images  of  objects  which  are  thrown 
and  delineated  on  the  retina,  and  which  are  never- 
thelefs  impreffed  with  fo  much  force*  that,  under 
certain  circumftances,  vefliges  of  them  remain  a 
considerable  time,  even  after  the  objects  them- 
felves  have  been  entirely  removed  from  the  eye. 


SECT. 


OF  THE  INTERNAL  SENSES.  19$ 


SECT.    XXII. 

OF  THE  INTERNAL  SENSES,  AND  OTHER  FACULTIES 
OF  THE  MIND. 

§     28l 

1  HROUGH  the  medium  of  thofe  ex- 
ternal fenfes,  of  which  we  have  hitherto  treated, 
ideas  are  conveyed  to  cur  nobler  part,  the  mind; 
for,  agreeably  to  the  tenor  and  fpirit  of  a  well- 
known  theorem,  nothing  can  enter  the  under- 
ftanding  fave  by  the  route  or  avenue  of  the  fenfes. 

§  282. 
For  the  purpofes  of  receiving  and  preferv- 
ing  the  ideas  thus  acquired,  by  the  aid  of  the 
fenfes,  and  alfo  for  making  the  belt  ufe  and  im- 
provement of  the  intellectual  (lock  received,  va- 
rious faculties  of  the  mind  contribute  their  united 
exertions.  Though  thefe  faculties  be,  (as  we 
have  already  had  occalion  to  obferve,  §  42.), 
widely  different  from  the  vital  energies  which 
refide  in  the  body,  neverthelefs,  by  means  of  the 
nervous  fyflem,  they  are  fo  clofely  connected  with 
thofe  corporeal  energies,  that  an  aftonifhing  in- 
tercourfc  is  thus  eftablifhed  and  fupported  between 
the  body  and  mind,  (§  211.) 

N  2  §  283. 


i9<i  OF  THE  INTERNAL  SENSES. 

§  283. 
The  firft  of  thofe  powers,  poffcfTing  indeed, 
apparently,  the  lowed  grade,  is  the  faculty  of 
Perception,  by  means  of  which  the  mind  is  ren- 
dered confeious  of  impreffions  made  on  the  dif- 
ferent organs  of  fenfe. 

§  284. 
This  faculty  is  aided  by  another,  of  better  rank 
and  higher  dignity,  namely,  attention,  which  fo 
directs  and  determines  the  mind  towards  any  idea 
when  once  excited,  as  to  rivet  its  thoughts  to  that 
object  alone. 

§  285. 
For  the  important  purpofes  of  preferving  ideas, 
which  have  been  already  perceived,  of  re-exciting 
them,  and  aflbciiuing  them  into  more  lively  and 
piclurefque  fpecies  of  imagery,  two  other  faculties, 
called  internal  fenfes,  are  brought  into  aclion  : 
thefe  are  memory  and  imagination,  two  powers, 
which,  though  nearly  allied  to  each  other,  may, 
notwithftanding,  be  readily  diftingnifhed  by  the 
following  characters  :  memory  appears  to  be  more 
fubfervient  to,  and  engaged  in,  the  reception  and 
retention  of  arbitrary  figns  of  things ;  whereas, 
imagination,  on  the  contrary,  wakes  up  rather  the 
very  images  of  things,  bellows  on  them  form  and 
colouring,  and  marfhals  them  under  the  view  of 

the 


OF  THE  INTERNAL  SENSES.  197 

the  mind,  as  if  the  objects  themfelvcs  were  again 
a&ually  prefent :  this  faculty  is  mure  particularly 
and  powerfully  exercifed  on  fuch  objects  as  are 
calculated  to  excite  fenfations  of  pleafure  or  difgu't. 

§  2S6. 
Upon  the  whole,  the  faculty  of  chafing  and 
refii/ing,  and,  (when  we  conhJer  the  matter  a 
little  more  minutely),  even  the  foundation  of  the 
whole  will  itfelf,  appear  to  relt  and  depend  en- 
tirely on  certain  agreeable  and  difagreeable  varie- 
ties of  fenfation. 

§  287. 
.From  the  fame  prolific  fource,  namely,  the 
imagination,  are  alfo  to  be  derived  the  affections 
or  commotions  of  the  mind,  to  which  we  fee  dif- 
ferent individuals  varioufly  fubjecled,  in  confor- 
mity to  the  countlefs  diverfities  of.exifting  tempe- 
raments (§  59.)  The  very  intimate  and  inilan- 
taneous  confent  of  thele  affections  with  certain 
functions  of  the  body,  appears  flrikingly  evident 
in  an  infinitude  of  examples  ;  thus,  for  inftance, 
there  is  fcarcely  a  fmgle  pafiion  of  the  mind,  which 
does  not  po  fie  is  confiderable  influence  over  the 
motion  of  the  heart,  the  appetite  for  food,  and  the 
powers  of  ciigc/lion, — not  to  defcend  10  a  minute 
fpecification  of  particular  effects,  fuch,  for  exam- 
ple,   as    the    acticn    of  fliame    in    giving   rife   to 

N  3  blujhing, 


198  OF  THE  INTERNAL  SENSES. 

blujhhig,  the  action  of  love  or  hatred  on  the  organs 
which  ferve  to  diftinguifh  the  fexes,  the  action  of 
anger  on  the  fecretion  of  bile,  &c.  &c. 

While  fpeaking  of  the  effe&s  produced  in  the 
economy  of  the  human  body,  by  the  commotions 
of  the  mind,  it  is  proper  to  obferve,  that  they 
may  be  divided  into  Jtimulant  and  fedative,  or 
into  thofe  which  excite,  and  thofe  which  deprefs. 

Of  the  former  defcript'o  1  are  joy,  love,  hope, 
anger,  &c. 

Of  the  latter,  fear,  forrow,  noftalgia,  and  other 
fpecies  of  permanent  defire  or  longing,  terror, 
envy,  Scq. 

§   288. 

Thofe  faculties  of  the  mind  hitherto  enume- 
rated, are  obferved  to  exift  in  brutes  as  well  as 
man,  though  the  latter  undoubtedly  poiTeffes  them 
in  by  far  the  highefl  degrees  of  ftrength  and  per- 
fection :  thus,  for  example,  in  none  of  the  inferior 
animals  do  we  difcover  a  memory  fo  extenfive  in 
its  range,  and  fo  powerful  in  its  tenacity  ;  in  none 
do  we  difcover  fuch  a  fplendid  brilliancy,  and 
glowing  warmth  of  imagination  ;  in  none  do  we 
difcover  fuch  an  unbounded,  and  fometimes  fatal, 
vehemence  of  mental  paflions,  &c. 

§  289. 


OF  THE  INTERNAL  SENSES. 


l99 


§  289. 
The  leading  prerogative  of  the  human  mind, 
confifts  in  this,  that  it  alone  pofTefTes  the  exclufive 
power  of  reafon,  by  means  of  which  it  is  able  to 
judge,  to  form  abftract.  ideas,  Sec.  and  which  exerts 
alfo  the  greatefl  influence  over  moil  cf  the  other 
faculties  of  the  mind,  in  place  of  this  divine 
power,  other  animals  are  endowed  with  various 
ifi/linds,  or  blind  and  involuntary  impulfcs,  which 
lead  them  to  the  performance  of  fuch  actions,  as 
are  fuitable  to  their  feveral  economies  and  modes 
of  life.  Of  thefe  inftincYive  impulfes  man,  on  the 
other  hand,  is  furnifhed  with  fcarcely  any,  fave 
that  which  prompts  him  to  participate  in  venereal 
gratifications. 

§    290. 
The  immenfe  and  (Iriking  difference  between 
animal  inftinft   and    human   reafon,   will    appear 
glaring  as  the  noon-day  light  to  him  who  eonfiders: 

That  inftincls  are  faculties  co-eval  with  birth, 
whereas,  on  the  other  hand,  the  ufe  of  reafon  is 
acquired  only  by  culture  and  education  : 


That  inftincls  remain  fiationary,  and  admit  of 
no  improvement,  whereas  the  expanfive  improve- 
ment and  exemfe  of  reafon,  are  literally  free  from 
circumfcripticm : 

N  4  That 


203  OF  THE  INTERNAL  SENSES. 

That  infiincts  are  fuited  only  to  the  deftined 
mode  of  life,  to  the  climate,  &c.  of  each  fpecies 
of  animals,  and,  on  this  account,  are  not  adequate 
to  the  exigencies  of  man,  who,  confined  to  no 
climate,  exclufively  reflricled  to  no  mode  of  life, 
is  deftined  to  be  an  inhabitant  of  the  world  at 
large  :  from  which  boundlcfs  and  fplendid  prero- 
gative, an  inconceivable  diverfity  of  wants  arife, 
which  fimple  inftincl:  is  too  weak! — far  too  weak 
to  fupply!  but  which,  the  powers  of  reafon,  from 
refources  equally  diverfified  as  the  emergencies 
themfelves,  are  able  to  fatisfy,  in  the  mod  ample 
and  complete  manner. 

Laftly,  another  high  prerogative  of  man,  de- 
pending on  the  powers  and  exercife  of  his  reafon, 
is  the  ufe  of  fpeech,  of  which  we  have  briefly 
fpoken  on  a  former  occafion  (§  154.)  This  in- 
valuable privilege  is  the  exclufive  boaft  of  man 
alone,  brutes  being  only  furnhhed  with  voice,  or 
a  power  of  emitting  found. 


SECT. 


OF  VOLUNTARY  ACTIONS.  201 


SECT.     XXIII. 


OF  THOSE  ACTIONS  OF  THE  BODY  WHICH  ARE 
SUBJECT  TO  THE  POWER  OF  THE  WILL. 


§    29I. 

JL  HE  nerves,  as  we  have  already  feen, 
are  fo  conftituted  as  to  perform  two  different 
functions  (§  215),  namely,  fenfation  and  motion. 
The  do&rine  of  the  former  we  have  already  con- 
sidered. It  yet  remains  to  add  a  few  obfervations 
on  thefubject  of  the  latter. 

§   292. 

The  motions  in  general  of  the  feveral  parts 
of  the  human  body,  are  ufually  divided  into  two 
claffes,  one  of  which  is  excited  and  governed  by 
the  power  of  the  will,  while  the  other  is  not  in 
any  meafure  fubjecr.  to  its  influence,  or  controul. 

For  examples  of  the  latter  clafs,  phyfiologifts 
commonly  refer  to  the  harmonious  a£lion  of  the 
heart,  and  likewife  to  the  perifialtic  motion  of  the 
inteflines  and  certain  other  vifcera,  &c. 

Inftances 


202  OF  VOLUNTARY  ACTIONS. 

Inftances  of  the  former  clafs  we  have  in  the 
motions  of  by  far  the  greater  part  of  the  other 
mufcles  of  the  body. 

Doubts  are  flill  entertained,  with  refpect  to  the 
real  nature  of  certain  motions  which  take  place  in 
the  human  fyftem ;  fuch  as  the  motions  in  refpira- 
tion,  in  fneezing,  in  the  tenfion  of  the  membrana 
tympani,  &c.  Thefe  are  by  fome  claffcd  with  the 
voluntary,  by  others  with  the  involuntary,  while 
others  again  refer  them  to  a  third  clafs,  called 
mixed  motions.- 


§   293. 

When  this  divifion,  however,  is  confidered  with 
a  little  more  fieadinefs  and  attention,  it  is  eafily 
perceived  to  be  embarrafled  with  fuch  momen- 
tous difficulties,  that  it  is  fcarcely  poffible  to 
ascertain,  and  mark,  with  definitude,  the  precife 
limits  between  the  claffes. 

For,  on  the  one  hand,  a  few  of  the  functions 
of  our  bodies,  over  which  the  will,  unaffifted  by 
other  powers,  may  be  faid  to  poflefs  no  command 
at  all,  may  notwithflanding  be  excited  and  brought 
into  action,  when  the  imagination  and  paffions  of 
the  mind  act  in  concert  with  the  will. 


On 


OF  VOLUNTARY  ACTIONS.  203 

On  the  other  hand  there  are  not  wanting 
inftances  of  mufcular  functions,  which,  though 
naturally  fubject  to  the  immediate  command  of 
the  will,  have,  notwithftanding,  been  rendered  in 
a  great  meafure  involuntary,  by  the  plaftic  power 
of  cujlom,  (the  influence  and  energetic  agency  of 
which,  on  animal  motions,  arc  indeed  of  the 
utmofl:  moment  and  importance.) 

§  294. 
Of  this  latter  defcription  are  thofe  kinds  of 
mufcular  motion,  which,  although  at  other  times 
fubjecT:  to  the  controul  of  the  will,  yet,  under 
certain  circumftances,  take  place  not  only  without 
the  confeioufnefs,  but  even  contrary  to  the  incli- 
nation of  the  mind. 

Thus,  for  example,  we  wink  contrary  to  our 
determination,  when  the  finger  of  a  friend  is 
haflily  approached  towards  our  eye,  although  it 
does  not  touch  it;  and  in  molt  perfons,  the  flexion 
of  the  little  finger  is  ufually  attended  with  a  fyn- 
chronous  flexion  of  the  ring  finger,  though  a  de- 
termination had  been  formed  to  preferve  the  latter 
entirely  unbent. 

Without  the  confeioufnefs  of  the  mind  we  fre- 
quently move  our  limbs,  even  when  wrapt  in  the 
mod:  profound  fleep. 

There 


204  OF  VOLUNTARY  ACTIONS. 

There  are,  on  the  other  hand,  examples  of 
mufcles,  which,  although  for  the  mod  part  per- 
fectly obedient  to  the  will,  yet  in  certain  cafes 
refufe  to  obey  its  commands.  To  this  head  we 
may  refer  the  difficulty  of  defcribing,  by  fyn- 
chronous  movements,  circles  in  contrary  directions, 
with  the  hand  and  foot  of  the  fame  fide,  together 
with  other  motions  of  a  fimilar  nature,  which, 
although  truly  voluntary,  and  extremely  eafy 
when  practifed  alone,  are,  notwithftanding,  per- 
formed with  the  utmoft  difficulty,  if  an  attempt 
be  made  to  alfociate  them  with  certain  other 
motions. 

§  295. 

With  refpect  to  thofe  motions,  which  phyfio- 
logiils  fuppofe  to  be  perfectly  exempt  from  the 
influence  of  the  will,  I  know  of  none  which  can 
be  clearly  and  unexceptionably  referred  to  this 
head,  fave  the  fpafms  of  the  uterus  in  the  labour 
of  parturition. 

With  refpect  to  the  pulfation  of  the  heart,  a 
very  remarkable  account  (lands  on  record  of  a 
Britifn  colonel,  who  pofTeffed  a  power  of  fuf- 
pending,  at  pleafure,  the  motion  of  both  the  heart 
and  arteries.  In  confirmation  of  the  truth  of  this, 
we  have  the  public  teflimony  of  Baynard  and 
Cheyne,  two  phyficians  of  the  higheft  reputation 

and 


OF  VOLUNRARY  ACTIONS.  205 

and  veracity,  who  were  themfelves  witneffes  to 
the  afloniming  phenomenon. 

That  the  motion  of  the  ftomach  may  be  volun- 
tary, (as  indeed  the  procefs  of  rumination  in 
general  feems  to  evince),  I  had  once  an  oppor- 
tunity of  afcertaining,  to  my  entire  fatisfa&ion,  in  a 
ruminating  human  fubjeft,  in  whom  this  retrogade 
or  reverted  motion  of  the  ftomach,  was  under  the 
mod  perfeft  fubjeclion  to  the  command  of  the 
will. 

Although  the  motion  of  the  iris  be  involuntary, 
in  by  far  the  greater  part  of  the  human  race,  I 
have,  notwithftanding,  been  favoured  with  an 
account,  fafficiently  authenticated,  of  a  man,  who 
poffeffed  a  power  of  voluntary  command  over  this 
membrane,  in  fuch  a  manner,  as  to  be  able,  by  a 
very  lingular  effort,  to  contract  the  pupil  of  the 
eye  even  in  a  weak  and  dull  light. 

There  are  indeed  a  great  variety  of  motions, 
which,  though  generally  performed  without  the 
influence  of  the  mind,  are  neverthelefs  voluntary 
in  certain  individuals,  cfpecially  if  a  high  degree 
of  attention,  and  a  vigorous  effort  of  imagination 
be  excited.  Thus,  I  have  known  men,  who  were 
able  at  any  moment,  to  produce  and  exhibit  on 
themfelves  a  fpafmodic  horripilation  of  the  fkin, 

and 


206  OF  VOLUNTARY  ACTIONS. 

and  alfo  to  renew  and  completely  revive  in 
themfelves  the  ideas  or  perception  of  certain  difa- 
grceable  fenfations. 

§   296. 

Perhaps  thofe  phenomena  may  be  fatisfa&orily 
explained  from  the  re-aclion  of  the  fenjorium, 
which  appears  to  be  indeed  as  powerfully  excited 
by  means  of  the  imagination  waking  up  and 
exhibiting  before  it,  the  image  of  an  active 
ftimulus,  as  by  the  Jlimulus  it/elf,  when  imprefling 
it  by  its  a&ual  prefence.  There  are  indeed  an 
infinitude  of  phenomena  of  the  animal  economy, 
which  admirably  correfpond  to  this  explanation; 
as  the  various  caufes,  for  example,  which  excite 
erections  of  the  male  penis,  &c. 

S  297. 

With  regard  to  voluntary  motions  in  general, 
it  may  be  proper  finally  to  obferve,  that  they  are 
among  the  primary  and  leading  chara&eriftics 
which  ferve  to  diftinguifli  the  animal  from  the 
vegetable  kingdom ;  for,  as  on  the  one  hand,  a 
power  of  voluntary  motion  is  never  obferved  to 
be  pofTefled  by  any  plant,  fo  on  the  other,  fuch  a 
power  conftitutes  an  effential  attribute  of  even  the 
raofl:  fimple  and  imperfect  genera  of  animals. 

§  298, 


OF  MUSCULAR  MOTION.-  207 

§  298. 
In  our  own  fyftems,  the  voluntary  motions  fur- 
nifh  the  mod  full  and  ftriking  evidence,  of  that 
intimate  and  truly  aitonifhing  harmony,  which 
fubfifts  between  the  mind  and  the  body.  Of  the 
exiftence  of  this  harmony  every  one  will  be  con- 
vinced, who  confiders  with  attention,  the  amazing 
celerity  with  which  fuch  diverfied  motions  fucceed 
each  other,  in  the  fingers  of  an  able  and  fkillful 
performer  on  the  violin,  or  in  our  organs  of 
fpeech,  while  we  are  engaged  in  converfation. 


SECT.    XXIV. 

OF  MUSCULAR  MOTION. 

§     299, 

X  HE  immediate  organs  of  by  far  the 
greater  number  of  the  motions  of  our  bodies,  are 
the  mufcles,  which  conftitute  the  principal  portion 
and  bulk  of  what  are  called  partes  fimilares. 

§    3°°- 
The  mufcles  are,  however,  diftinguifhed,  in  a 
particular  manner,  from  the  reft  of  the  fimilar 
parts,  by  a  two-fold  characleridic  j  one  depending 

on 


ao8  OF  MUSCULAR  MOTION. 

on  their  texture  ;  and  the  other  of  a  very  lingular 
nature,  derived  from  their  vital  energy. 

§   3OI« 
Their  texture  is  flefhy.,  compofed  of  a  peculiar 

fet  of  fibres,  of  a  very  pale  red  colour :  they  are 

fo  joined  together,  that  every  mufcle  confifts,   in 

the  firft:  place,  of  fibrous  cords,  thefe  cords  again, 

of  fmaller  bundles  of  fibres,  which  bundles,  by  a 

ftill   further  progreflive  divifion,    may  be  finally 

fepar'ated  and  refolved  into  flefhy  fibres  and  fibrils 

of  inconceivable  minutenefs. 

§  3°2- 
Each  mufcle  is  inclofed  in  a  cellular  fheath  or 
covering,  which,  pafiing  into  the  very  fubftance 
of  the  mufcle,  appears  to  be  interwoven  through- 
out the  whole  of  its  volume,  and  thus  forms  par- 
titions, firft  between  the  larger  lacerti,  then  be- 
tween the  fmaller  fafciculi  or  bundles,  and  laftly, 
between  the  fibres  and  more  minute  fibrils  them- 
felves. 

§  3°3- 
Befides  this  cellular  expanfion,  the  whole  tex- 
ture of  the  mufcles  is  alfo  interfperfed  with  an 
infinitude  of  blood-vcfiels  and  nervous  filaments  ; 
of  thefe,  the  latter  appear  to  deliquate  into  an 
infcrutable  pulp,  and  to  be  thus  very  intimately 
2  blended 


OT  MUSCULAR  MOTION.  209 

blended  along  with  the  mufcular  fibres  ;  bur  the 
former  are  fo  extenfively  and  minutely  interwoven 
among  thofe  very  tender  fibres,  as  to  paint  the 
whole  of  the  fleihy  parts  with  that  beautiful  crim- 
fon  dye,  by  which  they  are  uniformly  characlerifed. 
When  thefe  are  thoroughly  wafhed,  they  are 
again  fcflored  to  their  native  colour,  which,  as 
already  obferved  (§  301.),  is  fomewhat  pale-. 

§    3°4- 
Finally,  a  circumftance  common  to  mod  of  the 

mufcles  is,  that  they  terminate  in  tendons — parts, 
which,  though  likewife  of  a  fibrous  texture,  are 
notwithflanding  fo  extremely  different,  with  reflect 
to  colour,  flruclure,  eladicity,  &c.  that  their  entire 
difagreement  from  both  the  preceding  kinds  of 
fibres,  is  very  eafily  afcertained  and  demonftrated. 
Hence,  therefore,  we  are  enabled  fuccefsfully  to 
refute  the  opinion  of  thofe  phyfiologifb,  who  have 
crroneoufly  fuppofed,  that  the  tendinous ',  are  no- 
thing more  than  mere  continuations  of  the  mufcu- 
lar fibres.  To  the  adoption  of  this  opinion,  they 
have  been  inadvertently  led  by  attending  to  the 
following  phenomenon,  obfervable  in  the  mufcles 
of  infants  ;  namely,  if  we  compare  the  mufcular 
parts,  of  thefe  tender  fubjects,  with  thofe  of  adults, 
we  will  find  the  proportion  of  ilelh,  to  that  of 
ttndon,  greater  in  the  former  than  in  the  latter. 

vol.  i.  O  ?o<: 


210  OF  MUSCULAR  MOTION. 

The  other  exclufive  characteriftic  of  mufcle«, 
which  we  have  mentioned  (§  300.)  is,  the  irrita- 
bility  of  Haller.  Although  we  endeavoured,  on 
a  former  occaiion,  to  give  a  general  view  of  this 
vital  energy,  and  to  afcertain  the  difference  be- 
tween it  and  contrattility,  (§  44.)?  yet  it  may  not 
be  improper,  at  prefent,  to  purfue  the  inquiry  a 
little  further. 

S  306. 

This  irritability,  otherwife  called  vis  mufcularis, 
vis  injita,  or  vis  propria,  is  indeed  common  to 
all  the  mufcular  parts  of  our  bodies,  but  does  not 
refide  in  all  of  them  in  the  fame  degree,  fome  parts 
being  obferved  to  poffefs  a  much  higher  propor- 
tion of  it  than  others. 

The  principal  feat  of  this  energy,  where  it  moil 
plentifully  abounds,  is  the  hollow  mufclcs,  fub- 
fervient  to  the  vital  and  natural  functions  :  of 
thefe  mufcles,  the  heart,  as  was  obferved  formerly 
(§  H9-)j  poffeffes  the  higheft  degree  of  the  cha- 
rafterijlic  now  under  confideration  :  of  this  lad 
mentioned  organ,  the  internal  furface,  in  parti- 
cular, is  endowed  with  the  mofl  exalted  degree  of 
life,  and  is  by  far  the  mod  tenacious  of  irrita- 
bility. 

Next 


OF  MUSCULAR  MOTION.  211 

Next  to  i.he  heart,  in  point  of  this  prerogative, 
is  the  inteilinal  canal,  more  efpecially  that  portion 
cf  it  which  conftitutes  what  are  called  the,  final! 
inicjlines:  in  warm-blooded  animals,  this  part  of 
tl  e  tube  fomctimes  contracts  on  bein?  irritate  1, 
<:  a  after  the  heart  itfelf  has  become  incapable  of 
.notion. 

Next  in  degree  is  the  flomach, — next,  the  uri- 
nary bladder,  &c. 

Among  the  remaining  mufcles  of  the  fyflem, 
irritability  refides,  again,  in  a  very  finking  degree, 
in  thofe  actively  concerned  in  the  function  of 
refpiration,  as  the  diaphragm,  the  intercoftals, 
and  the  triangularis  Jlerni. 

Next  in  order  to  thefe  are  the  various  other 
mufcles  of  the  body. 

The  arteries  doubtlefs  poffefs  irritability,  though 
in  a  degree  far  inferior  to  what  exiils  in  the  parts 
jult  mentioned  (§  123.) 

This  vital  energy  refides  alfo  in  the  trunks  <s£ 
veins  contained  in  the  thorax,  (§  84.) 

In  a  degree  JIM  lower,  does  it  exift,  in  the  other 

parts  of  the  fanguiferous  veins,  if,  indeed,  thofe 

O  2  parts 


trz  OF  MUSCULAR  MOTION. 

parts  can  be  faid  to  pofTefs  any  genuine  irritability 
at  all  (S  128.) 

§  307. 

Haller  himfelf,  that  iiluflrious  defender  of  the 
doctrine  now  under  confiderauon,  appears  to  me 

to  have,  without  fuilicicnt  foundation,  attributed 
irritability  to  certain  parts  of  the  body,  which  are 
found,  indeed,  on  experiment,  to  be  endowed 
with  contractility  (§  50  feq.),  but  in  which  I  have 
never  been  able  to  difcover  any  indubitable  ttiii- 
monies  of  genuine  irritability. 

Among  thefe  parts  may  be  reckoned  the  lacleal 
veins,  the  fmall  glands,  the  pall-bladder,  the  uterus, 
the  dartcs  covering,  and  the  male  penis. 

On  no  better  foundation,  in  my  opinion,  is  irri- 
tability attributed,  by  others,  to  the  iris,  to  the 
external  furface  of  the  lun^s,  &c.  in  all  which 
parts  (if,  indeed,  I  be  capable  of  judging  rightly), 
there  exifrs  no  more  of  this  vital  energy,  than 
there  does  in  the  common  cellular  membrane,  and 
parts  compofed  of  it,  fuch,  for  inftance,  as  the 
common  integuments,  the  meninges,  the  pleura, 
the  peritoneum,  the  perioileum,  the  medullary 
membrane,  the  tendons,  the  aponeurofes,  &c. ; 
or  than  there  does  in  thofe  vifcera  compofed  of 
g  muine  parenchyma,  (§  27.),  fuch  as  the  liver, 

the 


OF  MUSCULAR  MOTION.  213 

the  fpleen,  the  kidneys,  the  fecundities,  the  brain, 
v, :  h  the  reft  of  the  nervous  fyftem,  8zc.  all  which 
parts,  as  they  are  thr  cughour,  completely  deftitute 
of  -nufcular  fibres,  (o  are  they  likev/ife  deftitute  of 
irritability,  which  refides  in  mufcular  fibres  alone. 

S   3oS- 

As  we  have,  thus,  on  the  one  hand,  feen 
mufcular  irritability  now  and  then  confounded 
with  cellular  contractility ,  (o  on  the  o:her,  certain 
celebrated  characters  have  lately  been  defirous  of 
ascertaining  and  eilablhhing  an  identity  between 
irritability  and  the  vis  ncr-vca. 

For  although  we  can  neither  deny  the  power- 
ful influence  of  the  nerves  on  mufcular  motion^  (of 
which  we  will  fpeak  a  few  words  prefently),  nor 
exhibit  the  fmalleft  fibril  of  mufcular  flefh,  per- 
fectly deftitute  of  the  pulp  of  evanefcent  nerves, 
yet  thefe  circumftances  are  not  fufficiently  mo- 
mentuous  to  compel  us  to  a  dereliction  of  the 
opinion,  that  irritability  is,  in  its  own  nature,  as 
widely  and  eiTcntia'Iy  different  from  riae vh mrve.a 
as  it  is  from  contracliUty.  On  the  one  hand, 
this  energy  is  wanting  in  all  parts  not  -mufjular, 
although  they  be  Supplied  with  the  utmoft  profu- 
fion  of  nerves,  as  the  lldn,  all  the  nervous  vifcera, 
£ic;  whereas,  on  the  other,  we  are  not  able  to 
produce  any  portion  of  true  mufcu'ar  (lc(h,  v»here 
O  3  to  6 


214  OF  MUSCULAR  T-IOTIOI-:. 

the  genuine  and  obvious  phenomena  of  irritability 
do  not  exhibit  themfrlves.  From  a  clofe  and 
impartial  confiJcration  of  the  foregoing  argu- 
ments, befides  a  great  number  of  others  which 
might  be  advanced,  it  appears  more  confonant  to 
reafon  and  found  induction,  to  attribute  the 
lingular  phenomena  of  irritability  to  the  equally 
fincnilar  texture  of  mufcular  fibres,  than  to  refer 
them  to  the  nerves,  which,  in  fc  many  other  parts 
of  the  body,  are  as  minutely  distributed  as  they  are 
through  the  mufcles,  and  yet  do  not  generate  and 
exhibit,  in  thofe  parts,  the  fainted:  fhadow  of  real 
irritability.  I  fay  nothing  of  the  weighty  argu- 
ments which  might  be  drawn  from  the  following 
well-founded  pofition,  viz.  that  no  fteady  propor- 
tional relation  is  obferved  to  exift,  between  the 
degree  of  irritability  in  any  part  of  the  body,  and 
the  quantity  of  nerves  with  which  it  is  fupplied. 

§  3°9- 
With  refpect  to   the  extreme  terminations   of 

the  nerves,  which  are  well  known  to  exert  an 
influence  over  the  mufcles,  the  following  appears 
to  be  the  mod  rational  conclufion,  viz.  that  they  may 
be  conlldered  as  remote  or  exciting  camfes  of  muf- 
cular motion,  but  fhould  not  be 'confounded  with 
the  proximate  or  efficient  cnufe,  which  is  indeed 
irritability  alone,  and  that  refiding  exclufively  in 
the  mufcular  fibres.  - 

The 


OF  MUSCULAR  MOTION.  215 

The  pafiions  of  the  mind,  for  example,  aft  on 
the  fenforium,  this  again  re-acts  on  the  nerves  of 
the  heart,  in  fuch  a  manner,  as  to  excite  its  irrita- 
bility, and  thus  produce  palpitations  and  other 
irreguiar  motions  of  this  organ. 

The  will  acts  on  the  fenforium,  this  re-acts 
again  on  the  nerves  of  the  arm,  thefe  nerves  in 
like  manner  operate  immediately  as  remote  caufes 
in  exciting  mufcular  motion,  which,  notwith- 
ftanding,  depends  ultimately  for  its  exiftence  on 
irritability  itfelf. 

§  V°- 
This  diftinction,  of  the  two  kinds  of  caufes 
which  concur  in  the  production  of  mufcular 
motion,  is  indeed  fully  authorifed  and  fanctioned 
by  actual  experiments:  from  a  variety  of  thefe  it 
appears,  that  certain  parts  of  the  animal  fyftem 
have  been  oftentimes  rendered  paralytic,  by  cutting, 
or  inclofing  in  ligatures,  the  nerves  leading  to  them, 
while  they  have,  notwithstanding,  frill  continued  to 
retain  their  irritability  for  a  long  time  afterwards. 

In  what  degree  the  blood,  with  which  the 
mufcles  are  very  abundantly  fupplied,  contributes 
to  their  action,  is  not  yet  clearly  and  fatisfactorily 

afcertained. 

O4  It 


216  OF  MUSCULAR  MOTION. 

It  appears,  however,  from  an  experiment  of 
Steno,  ih.u  a  paralyfh  of  the  lower  extremities 
may  be  generally  produced,  by  paffing  a  ligature 
round  the  aorta  in  its  defcent  behind  the  abdo- 
minal cavity. 

Befides  thefe  common  inherent  energies  of  the 
mufdes,  which  have  hitherto  been  the  fubjecls  of 
our  confidenuion,  they  poffefs  alio  certain  fpecific 
and  adventitious  peculiarities,  ariiing  from  varieties 
in  their  figures,  fituations,  Szc.  by  thefe  peculia- 
rities they  are  adapted,  and  rendered  completely 
adequate,  to  the  nice  performance  of  their  feveral 
functions. 

S  3l3- 
From  the  contemplation  of  this  circumflance, 
mufcles  are  ufually  divided  into  hollow  and  folid  : 
the  former  of  thefe,  as  we  have  already  feen,  not 
being  in  immediate  fubjedtion  to  the  command  of 
the  will,  are  particularly  deflined  to  the  perfor- 
mance of  the  vital  and  natural  functions,  and 
cannot,  therefore,  be  further  treated  of  in  this 
place,  where  we  are  confidering  what  are  called 
voluntary  mufcles,  which  are  more  efpecially  fub- 
fervient  to  tint  order  denominated  the  animal 
fu  nil  ions. 

§  3M- 


OF  MUSCULAR  MOTION.  217 

Between  thefe  lad-mentioned  mufcles  them- 
felves,  there  occur  again  very  ftriking  diverfities. 
For  to  fay  nothing  of  the  varieties  in  their  relative 
magnitudes,  they  differ  extremely  from  each  other 
in  the  difpofition  of  their  lacerti  and  fafciculi,  in 
the  direction  of  their  fibres,  but  more  efpecially 
in  the  habit  and  proportional  relation  of  their 
fleihy  and  tendinous  parts,  and,  finally  in  their 
courles,  their  infertions,  &C. 

§   3l5- 
Neverthelefs,  in  by  far  the  greater  part  of  the 

fiifform    or    tapering    mufcles,    their    figures  are 

more  or  lefs  oblong,  (o  that  their  flefhy  bellies 

terminate  at  each  end  in  tendinous  cords.     Thefe 

cords,  which  are  inert  and  perfectly  deftitute  of 

irritability,   being    attached  to,  and   infrrted    in, 

bones,  ferve   the   neceffary    purpofe    of  moving 

them  after  the  manner  of  levers. 

§    3l6- 
As  there  are,  however,   a  few  mufcles  in  the 

body  entirely  defliture  of  tendons,  fuch  as  the 
latijjimus  colli ;  fo  there  are,  in  like  manner,  a  few 
no:  attached  to  bones,  namely,  the  mufcle  laft 
mentioned,  the  cremajler  mufcle,  as  it  is  generally 
called,  the  azygos  uvula,  and  mod  of  thofe  which 
move  the  ball  of  the  eye. 

§  3*7- 


218  OF  MUSCULAR  MOTION. 

§  3*7- 
By  the  co-operation  and  combined  aid  of  all 

thofe  energies,  (as  well  the  common,   §   305,  as 

the  proper,  §  312),  with  which  the  mnfcles  are 

furnifhed  thefe   inftruments  of  motion  are  fitted 

and  completely  qualified  for  the  performance  of 

their  feveral  actions,  which  may,  in  like  manner, 

be  alfo  divided  into  common  and  proper. 

§3;8' 

During  their  common  action,  which  avifes 
immediately  from  irritability,  and  occurs  in  all 
mufcles,  their  flefhy  portions  become  fliorter, 
more  rigid,  and,  for  the  mofl  part,  unevenly  and 
fomewhat  angular.  It  alfo  appears  irom  the 
celebrated  experiment  of  Gliffon,  that  they  fuffer 
at  the  fame  time  a  flight  diminution  in  point  of 
magnitude. 

We  are  indeed  prevented  from  joining  Jo. 
and  Dan.  Bernouille,  and  other  mathematical 
phyficians,  in  an  attempt  to  reduce  the  meafure 
of  this  diminution  to  common  calculation,  firft,  by 
the  immenfe  difference  in  this  refpecl,  which  is 
obfervable  between  the  hollow  and  folid  mufcles, 
and  fecondly,  by  the  diverfity  which  alfo  occurs, 
on  the  fame  point,  between  thefe  latter  mufcles 
themfelves; — not  to  mention  various  other  diffi- 
culties, which  obflrucl  the  road  to  fuccefs. 

S   3*9- 


OF  MUSCULAR  MOTION.  219 

§3I9- 
The  proper  or  fpecific  actions  of  the  mufcles, 
(§  3l7-)>  correfpond  precifely  to  their  fpecific 
energies  ;  from  whence  it  naturally  and  fponta- 
neoufly  follows,  that  thefe  actions  are  marked 
with  fuch  an  infinitude  of  varieties,  as  to  render  it 
literally  impoflible  to  reduce  them  to  any  general 
laws,  or  to  arrange  them  under  any  well-defined 
orders  and  genera. 

With  regard  to  the  general  principle,  commonly 
taught  and  adopted  on  this  fubject,  viz.  that  every 
mufc'-j  while  in  aciion,  draws  the  more  moveable 
part  to  which  it  is  attached,  towards  that  which  is 
more  permanent,  it  ought  to  be  confidered,  fas  has 
been  veryjuftly  obferved  by  the  fagadous Window) 
in  a  relative  point  of  view,  and  is  indeed  fubjecl: 
to  a  variety  of  limitations.  Thus,  for  example, 
the  two  parts  to  which  a  mufcle  is  attached,  may 
be  rendered,  each  more  moveable  than  the  other, 
in  alternate  vicifTnudes,  accordingly  as  the  one  or 
the  other  is  fked  and  rendered  ftationary,  by  the 
joint  aciion  of  other  co-operating  mufcles. 

As  to  the  aftion  of  the  flexor  mnfclcs,  it  ou^ht 
to  be  cftimated  on  contrary  principles,  and  a  dif- 
ferent opinion  formed  refpecling  it.  Although 
thefe  mufcles,  for  the  moft  part,  predominate  fo 
much  over  their  antagonifb,  the  extenfors,  that 

when 


22o  OF  MUSCULAR  MOTION. 

when  the  body  is  in  a  ftate  of  perfeft  quietude 
and  reft,  the  arms,  fingers,  Sec.  are  under  a  gentle 
degree  of  flexion,  yet  thefe  parts  do  not  appear  to 
be  drawn  into  this  ftate  and  pofuion  by  any  aftual 
force,  but  rather  in  confequence  of  a  voluntary 
relaxation  of  their  extenfor  mufcles,  by  means  of 
which,  thofe  mufcles,  fubfervient  to  the  flexion  of 
the  parts,  are  left  at  liberty  to  aft  without  oppo- 
fiton  or  refiftance. 

§  32°- 
To  all  the  foregoing  confederations,  it  appears 
proper  to  add,  in  the  laft  place,  that  each  niufcle 
pofTeffes  a  peculiar  and  fpecific  mechanifm,  by 
means  of  which  it  is  adapted,  in  the  moft  complete 
manner,  to  the  performance  of  the  various  motions 
of  its  immediate  deftination. 

Befides  the  peculiar  advantages  which  the 
mufcles  feverally  derive  from  their  determinate 
figures,  their  aftions  are  alio  promoted  by  a  variety 
of  other  concomitant  aids,  fuch,  for  inftance,  as  the 
annular  ligaments  by  which  they  are  furrounded  ; 
the  fat,  in  which  a  great  number  of  them  are 
imbedded  ;  the  lymphatic  dew  with  which  they 
all  abound  ;  and,  what  ought  to  have  been  men- 
tioned in  the  very  firft  inftance,  the  confoimation 
of  the  fkeleton  itfelf,  efpecially  as  far  as  the  fame 
relates  to  the  ftrufturc  of  the  apophyfes,  and  the 

articulation 


OF  MUSCULAR  MOTION.  ait 

articulation  of  the  joints :  under  the  fame  head  of 
auxiliaries  to  the  mufcles,  may  be  alfo  arranged 
certain  entire  bones,  as  the  patella,  and  offa, 
fefimoidea,  of  fimilar  ftruchires  and  ufes,  which 
nature  appears  to  have  very  wifely  adapted  and 
deftined  to  facilitate  the  motions  of  particular 
mufcles. 

321. 

By  thefe  diverfified  and  numerous  aids,  has 
nature  made  compenfation  for,  or  at  leafl  very 
ccnfiderably  diminifhed,  that  inevitable  lofs  of 
power,  which  neceiTarily  arifes  from  the  confor- 
mation and  ftature  of  the  whole  body.  The 
acutenefs  of  the  angles  formed  by  the  insertions 
of  a  great  many  mufcles,  and  the  vicinity  of  thefe 
infertiens  to  the  centres  of  motion,  mav  be  brought 
forward  as  incontrovertible  teftimonies  in  favour 
of  fuch  a  lofs  of  power,  which  would  not  have 
been  fuftained,  had  the  tendinous  cords  been  in- 
ferted  at  greater  diftances  from  the  centres  of 
motion,  or  in  fuch  directions,  as  to  have  formed 
more  obtufe  angles. 

§  322- 
To  our  bodies,  thus  furnifhed  with  about  four 
hundred  and  fifty  mufcles,  together  with  a  few 
occalional  fupernumeraries,  (arifing  from  fexual 
and  individual  varieties),  two  advantages  of  the 
urmofl  magnitude  and  importance  are  very  obvi- 

oufly 


222  OF  MUSCULAR  MOTION. 

oufly  derived.  Firft,  in  confequence  of  this  beau- 
tiful and  complicated  fyftem  of  organs,  not  only 
our  individual  members,  but  alfo  our  whole  bo- 
dies, are  rendered  capable  of  the  mod  aftonifhing 
agility,  in  point  of  motion  ;  and  Jecondly^  from 
the  fame  fource,  we  derive  fuch  remarkable  de- 
grees of  ftrength,  as  qualify  us  to  bear,  without 
injury,  the  moft  arduous  fpecies  of  labour  and 
fatigue.  Thefe  two  momentous  advantages  de- 
pend, indeed,  in  part,  on  a  perfect  ftate  of  the 
mufcles,  to  which,  no  lefs  than  to  a. perfect  ftate 
of  the  bones,  we  arrive  by  degrees,  as  youth 
advances  towards  maturity;  but  they  are  alfo,  in 
part  acquired  by  a  frequency  of  ufe  and  exercife. 
The  powerful  influence  which  thofe  two  latter 
circumftances  pofTefs  and  exert  over  the  mufcles, 
in  ftrengthening  them  and  rendering  them  capable 
of  the  utmofl  agility  of  motion,  is  flrikingly  de- 
monstrated by  numerous  examples  of  rope-walkers, 
of  dancers,  of  runners,  of  wreftlers,  of  boxers, 
and  of  thofe  robuft  barbarians,  who  conftituted 
the  glory  and  boafl  of  former  ages. 


SECT. 


OF  SLEEP.  223 


SECT.     XXV. 


OF    SLEEP. 


§  323- 

1  HOSE  two  fprcies  of  nervous  acYion, 
(die  hiitory  of  which  we  have  dow  completed) 
that  have  for  their  ultimate  ends  fenfation  and 
motion,  are  fo  reduced  and  debilitated  by  the 
divcrfified  exercifes  of  the  day,  that  repofe 
by  night  becomes  abfulutely  neceiTary,  for  the 
purpofe  of  refrefhing  their  declining  vigour 
and  energy,  which  Jkcp  alone,  the  image,  or  fern- 
blanu  of  gelid  death,  is  able  compleiely  to  reftore. 

§  3*4- 

Sleep  is  a  fun&ion  perfectly  periodical,  which 
fufpends,  as  it  were,  for  a  time,  all  intcrcourfe 
and  communication  between  the  mind  and  body. 
The  various  phenomena  of  this  function,  fome  of 
which  (hall  be  immediately  enumerated,  appear  to 
declare,  with  no  fmall  force  of  evidence,  in  favour 
of  the  exigence  of  a  nervous  fluid. 

§  3*S- 
Befides  a  variety  of  ether  cirenmftances,  we 

may  here  enumerate  as  precurfors  and  harbingers 

of 


224  OF  SLEEP. 

of  fleep,  a  fluggilhncfs  and  gradually  increafing 
dullncfs  of  the  external  fenfes,  together  with  a 
relaxation  of  molt  of  the  voluntary  mufcles, 
efpecially  fuch  as  are  of  confiJerable  length.  To 
thefe  may  be  added  a  congeflion  of  the  venous 
blood  in,  and  near,  the  heart,  and  an  effort  to 
remove  the  uneafmefs  thence  arifing,  by  the  aid 
of  yawning.  Finally,  the  only  additional  pre- 
cursor to  be  mentioned  at  prefent,  which  appears 
to  conflitute  the  very  ijih/nus,  as  it  were,  between 
the  waking  and  fleeping  dates,  and  the  immediate 
tranfition  of  the  former  into  the  latter,  is  a  pecu- 
liar fpecies  of  tranilent  delirium. 

§   326. 

The  following  are  what  conflitute  the  principal 
phenomena  of  fleep,  when  that  flate  has  actually 
occurred:  the  animal  functions  are  wholly  fuf- 
pended  from  action,  while  aimed  all  the  others  are 
at  the  fame  time  performed  in  a  more  fluggifh  and 
torpid  manner;  thus,  in  fubjecls  buried  in  fleep, 
all  other  circumftances  being  alike,  the  pulfe  is 
flower,  and  the  heat  of  the  body  fomewhat 
diminifhed  ;  perfpiration  is  alfo  lefs  plentiful  ; 
digeflion  lefs  powerful;  and  (if  the  occafional 
difcharge  ofthefemen  mafculinutn  be  excepted) 
all  the  excretions  are  fupprelTed,  8:c. 

1  §  327> 


OF  SLEEP.  22$ 

§  3*7- 
The  remote  caufes  which  induce  fleep  are  very 
plain  and  obvious.  For  to  fay  nothing  of  narcotic 
fubftances  themfelves,  we  may  confider  as  very 
energetic  caufes  in  the  production  of  this  ftate,  all 
ivafte  of  the  animal  powers  by  means  of  preceding 
fatigue,  by  watching,  &c.  To  thefe  we  may  fab- 
join  the  influence  of  cuftom,  together  with  dark- 
nefs,  filence,  reft,  &c.  which  appear  indeed  to 
derive  their  fomnifcrous  powers  from  the  fame 
fource;  we  may  alfo  further  add,  gentle,  uniform, 
and  conftant  impreffions  acting  on  any  of  the 
fenfes,  fuch,  for  inftance,  as  the  foft  murmurings 
of  the  rill,  or  the  appearance  of  a  harvefl:  field, 
agitated  and  thrown  into  wavy  undulations,  by  the 
mild  fannings  of  the  weftern  breeze,  &c.  Under 
the  fame  head  of  remote  caufes  we  may  alfo  con- 
fider, full  meals,  and  intenfe  cold  acting  on  the 
body,  together  with  a  variety  of  other  circum- 
ftances,  tending  to  derive  the  blood  from  the 
encephalon,  as  pediluvia,  clyfters,  and  profufe 
hemorrhages,  &e. 

§  3*7- 

Thofe  remote  caufes  which  we  have  mentioned 
in  the  latter  part  of  the  preceding  paragraph,  are, 
of  themfelves,  fufficient  to  conduct  us  to  the  proxi- 
mate caufe,  which  appears,  from  the  beft  evidence 

vol.  1.  P  that 


2  26  OF  SLEEP. 

that  can  be  collected  on  the  fubjecl,  to  confifl  in 
a  diminution  of  the  column  of  blood  that  goes  to 
fupply  the  encephalon. 

That  this  is  indeed  the  proximate  caufe  of  fleep, 
is  powerfully  illuflrated  and  confirmed,  by  a  very 
fingular  and  ftriking  phenomenon,  which  I  had. 
once  an  opportunity  of  obferving  in  a  living 
human  fubjeft,  whofe  cafe  has  been  already  men- 
tioned on  another  occafion.  As  often,  and  as 
long,  as  this  perfon  indulged  himfelf  in  fleep,  his 
brain  fubfided  and  continued  in  a  flate  of  confi- 
derable  collapfe,  but  during  his  waking  hours 
throughout  the  day,  this  organ  became  again 
turgid  and  diflended  in  confequence  of  a  more 
copious  afflux  of  blood. 

As  an  additional  argument  in  fupport  of  the 
fame  caufc,  we  may  obferve,  that  morbid  watch- 
fulnefs,  on  the  other  hand,  ufually  arifes  from 
congeftions  of  blood  in  the  region  of  the  brain. 

§  329. 
The  quantity  of  fleep  neceflary,  depends  in  a 
great  meafure  on  varieties  in  age,  habit  of  body, 
temperament,  &c.  The  general  refult,  however, 
of  all  the  exifting  evidences  on  this  fubjedt, 
appears  to  be,  that  a  longer  indulgence  in  fleep  is 
cither  a  concomitant  of  imbecility  (as  is  the  cafe 

in 


OF  SLEEP.  227 

in  tender  infants,  and  fubjefts  far  advanced  in 
years),  or  a  very  exuberant  fource  of  fatuity  and 
dullnefs. 

§  330- 
We  rife  from  fleep  with  renovated  powers,  and 
our  return  into  the  living,  and  completely  waking 
ftate,  is  accompanied  with  fymptoms  and  pheno- 
mena very  fimilar  to  thofc  which  attended  our 
tranfition  from  this  ftate  into  that  of  fleep:  we  are 
attacked,  for  inftance,  by  a  yawning,  accom- 
panied for  the  moft  part  with  more  or  lefs  of  a 
ftretching,  we  are  a!fo  affected  by  a  certain  dull- 
nefs and  torpidity  of  the  fenfes,  &c. 

§    33l- 
The  caufes  which  roufe  into  wakefulness,  ap- 
pear to  correfpond  exactly  with  thofe  productive 
of  fleep. 

The  proximate  caufe  will  be  the  return  of  a 
more  copious  column  of  blood  into  the  ence- 
phalon. 

The  remote  caufes,  befides  the  power  of 
cuftom,  which  is  confeffedly  very  great,  confift  of 
an  immenfe  variety  of  ftimuli,  that  may  be  divided 
into  external  and  internal.  The  external  are 
calculated  to  excite  the  flumbering  fenfes,  while 
P  2  the 


228  OF  SLEEP. 

the  internal  act  either  immediately  on  the  body 
itfelf,  as  the  didenfion  of  the  urinary  bladder;  or 
imprefs  the  nervous  fyftem  through  the  medium 
of  the  imagination,  the  mode  in  which  dreams 
operate. 

S  332> 
Dreams  are  light  fportings  of  the  imagination, 
in  which  it  recalls  the  images  of  things  formerly 
perceived,  and  appears  to  exercife  and  bufy  itfelf 
in  arranging  and  combining  them  into  the  moll 
fantaftical  reprefentations. 

I  have  never  been  able  to  difcover  the  flighted 
veflige  of  this  faculty  in  new-born  infants  pre- 
vioufly  to  the  third  month  after  birth. 

There  are  alfo  various  examples  of  adults  who 
explicitly  declare,  that  they  have  no  knowledge 
cf  dreams,  having  never  been  troubled  by  them. 

Thofe  vifions  of  the  night  are,  for  the  moft 
parr,  indeed,  confufed  and  irregular;  but  they 
arc,  notwithftanding,  fometimes  marked  with 
ailoniming  veftiges  of  reafon. 

The  influence  cf  flimuli  acting  on  the  body  is 

truly  great  in  the  production  of  dreams:  thus  the 

famulus   of  the  ma'e  femen  gives  rife  to  luflful 

2  ideas; 


OF  SLEEP.  229 

ideas ;  the  ftimulus  of  an  exceflive  plethora  calls  up 
images  of  a  frightful  and  terrifying  nature,  &c.  We 
have  even  received  a  well  confirmed  account  of  a 
man,  to  whom,  while  afleep,  his  friends  could  fug- 
ged whatever  vifions  they  pleafed,  by  communi- 
cating to  him  the  fubjecT:  and  matter  of  the  dream 
in  a  foft  and  gentle  tone  of  voice.  This  appears 
however,  to  belong  rather  to  a  preternatural  (late, 
confifting  of  fomnolency  and  wakefulnefs,  ot 
which  that  truly  morbid  affeftion  of  the  fomnarji' 
bulantes,  or  thofe  who  walk  in  their  fleep, 
conftitutes  alfo  another  variety. 

It  is  neceiTary  previoufly  to  the  final  conclufion 
of  this  fubjeft  to  obferve,  that  Locke  and  others 
have  thought  proper  to  confider  all  dreams  as 
belonging  to  this  mixed  or  compound  (late. 


END  OF  THE  FIRST  VOLUME. 


ELEMENTS 


OF 


PHTSIOL  0  GT. 

SECTION    XXVI. 
OF  FOOD,  AND  THE  APPETITE  FOR  IT, 


§  33^ 

AS  the  wafte  of  the  animal  powers  is 
again  reftored  by  fleep,  fo  in  like  manner  the  in- 
ceilant  lofs  of  the  natural  powers,  and  even  of  the 
very  elementary  parts  of  the  body,  is  repaired  by 
frefh  and  repeated  fupplies  of  food. 

S  333- 
To  the  acquifition  and  ufe  of  this  food  we  are 

forcibly  led  by  the  frequent  and  irrefiftable  calls 
of  nature.  Thefe  calls,  though  widely  different 
from  each  other  in  their  natures,  tend  notwith- 
standing to  the  final  accomplishment  of  the  fame 
end  :  they  confift,  on  one  hand,  of  the  infupport- 
vol.  ii.  A  able 


2  OF  FOOD  AND  APPETITE. 

able  torments  of  hunger  and  thirjl ;  and  on  the 
other,  of  the  very  pleafing,  but  no  lefs  powerful, 
allurements  of  appetite. 

§   334- 
The  ftimulus  of  hunger ,  fome  phyfiologifts  have 

fjught  for  in  the  mutual  friction  between  the  rugae 

of  the  ftomach  when  empty  ;  others  in  that  which 

appears,  indeed,  to  be  of  primary  importance  in 

giving  birth  to  this  potent  fenfation,  namely,  not 

only  in  a  more  copious  fecretion  and  afflux  of  the 

humours  difcharged  into  the  firft  pafTages,   mere 

efpe.  ially  of  the  faliva,  the  pancreatic  juice,  and 

the  bile,  but  alfo  in  a  certain  degree  of  morbid 

acrimony,  with  which  thefe  fame  humours  are  apt 

to  be  contaminated,  unlefs  fuch  a  ftate  be  guarded 

againfl  by  regular  fupplies  of  nourishment. 

§  335- 
Thirjl  is  a  diftrefTing  fenfation,  arifing  princi- 
pally from  a  very  troublefome  drynefs  of  the  fau- 
ces and  efophagus  ;  and  alfo  from  a  peculiar  im- 
prefiion  produced  by  taking  in  acrid,  but  more 
efpecially  faline,  fubflances. 

§  336- 
With  refpect  to  the  abfolute  necejjity  of  fatisfy- 

ing  and  removing  thele  ftimuli,  no  fixed  and  pofi- 

tive  rule  can  with  propriety  be  laid  down,  as  fuch 

neceflity 


OF  FOOD  AND  APPETITE.  3 

necefiity  is  doubtlefs  rendered  more  or  lefs  urgent 
by  varieties  in  age,  habit  of  body,  and  more  efpe- 
cially  by  the  power  of  cuftom.  From  a  general 
confideration  of  this  fubject,  however,  the  refult 
appears  to  be,  that  an  adult  and  healthy  perfon, 
who  is  under  no  undue  imprcflions  or  influence, 
(in  whom,  for  inftance,  thofe  aiTuafive  calls  of  na- 
ture are  neither  filenced  by  the  louder  ravings  of 
enthufiaflic  fanaticifm,  nor  by  other  preternatural 
caufes)  cannot  refrain  from  the  ufe  of  food,  for 
even  one  whole  day,  without  a  very  great  proflra- 
tion  of  ftrength  ;  and  can  feldom  fad  for  more  than 
eight  days  without  incurring  the  utmoft  hazard  of 
life. 

§  337- 
With  regard  to  drink,  although  a  defire  for 
this  appears  to  urge  with  the  greater  vehemence 
and  intenfity  of  the  two,  it  is,  notwithftanding, 
much  lefs  necefTary  to  life  and  health  than  the  ar- 
ticle of  food.  This  we  infer,  with  apparently 
ftrict.  propriety  and  truth,  not  only  from  numerous 
fpecies  of  warm-blooded  animals,  as  mice,  quails, 
&c.  that  are  never  impelled  by  neceflf-ty  to  the  ufe 
of  drink,  but  alfo  from  actual  examples  of  certain 
individuals  of  the  human  race,  who  have  conti- 
nued, through  a  long  feries  of  time,  in  the  enjoy- 
ment of  life,  health,  and  fpirits,  without  recourfe- 
to  the  ufe  of  drinks  of-  any  kind. 

A  2  §   y^. 


4  OF  FOOD  AND  APPETITE. 

§  338- 

As  to  food,  controverfies  have  exifted  refpe&ing 
the  kind  moft  proper  to  fatisfy  the  internal  calls 
of  our  nature :  whether,  for  example,  the  frruc- 
ture  and  conftitution  of  the  human  body  corres- 
pond moil:  perfectly  w  ith  food  taken  from  the  ani- 
mal, or  with  that  derived  from  the  vegetable, 
kingdom  ;  and  which  of  thefe  two  kinds  of  fub- 
ftances  nature,  therefore,  defigned  to  constitute 
the  aliment  of  man  ? 

§  339- 
That  man  is  by  nature  an  herbivorous  animal, 
Rouffeau  attempted,  with  a  great  degree  of  acute- 
nefs,  to  prove,  not  only  by  arguments  taken  from 
the  figure  of  his  teeth,  and  the  length  of  his  in- 
teftines,  but  by  the  further  confideration,  that  wo- 
man is  naturally  uniparous,  and  furnilhed  with 
two  mammas,  &c. ;  to  all  which  might  be  added, 
a&ual  examples  of  rumination  having  been  per- 
formed by  human  Subjects,  a  procefs  well  known 
to  belong  exclufively  to  herbivorous  animals. 

Thofe,  on  the  contrary,  who,  with  Helvetius, 
confider  man  as  a  carnivorous  animal,  attempt  to 
fupport  their  opinion  by  the  fhortnefs  of  his  intef- 
tinum  c<zcum,  and  other  arguments  of  a  fimilar 
nature. 

§  340. 


OF  FOOD  AND  APPETITE.  y 

§  34°- 
But  from  more  accurate  obfervation,  and  a 
more  minute  inveftigation  of  the  fubjeft,  it  ap- 
pears, that  nature  did  not  intend  to  reftridt  man 
to  the  exclufive  ufe  of  either  the  one  or  the  other 
of  thofe  kinds  of  aliment,  but  more  indulgently 
deflined  him  to  a  free  participation  of  both.  That 
this  is  indeed  the  kind  deflination  of  man  with  re- 
flect to  the  nature  of  his  food,  we  very  naturally 
infer  from  his  teeth,  efpecially  the  molarcs,  and  the 
conformation  of  his  inteftines,  briefly  mentioned 
above,  poflfeffing  a  middle  (fate  between  the  fame 
parts,  as  they  exift  in  carnivorous  and  in  herbivo- 
rous animals.  This  prerogative  of  man  is,  how- 
ever, dill  more  forcibly  demonftrated,  by  the  na- 
ture of  the  artieulation  which  connects  the  con- 
dyles of  the  lower  jaw  to  the  ojfa  temporum  in  hu- 
man fubjecls. 

§  341. 
If  the  obfervations  be  true  (and  they  furely 
cannot  be  doubted)  which  we  dated  on  a  former 
occafion,  refpecting  the  high  privilege  of  man,  in 
being  by  far  better  calculated  than  other  animals 
for  traverfinsr  an  extenfive  ran  ire  of  climate  on 
the  globe  we  inhabit,  it  from  thence  fpontane- 
oufly  follows,  that  he  would  have  been  indeed 
very  illy  accommodated,  in  being  folely  reftric~red 
either  to  the  one  or  the  other  of  the  above  kinds 
A3  of 


6  OF  FOOD  AND  APPETITE. 

of  food :  for  as  fome  regions  of  the  globe  afford 
animal,  and  others  vegetable  food  alone,  the  ob- 
vious and  unhappy  refult  of  fnch  an  exclufive  re- 
ftri&ion  would  have  been,  that  man,  though  cal- 
culated and  deftined  to  refide  in  all  latitudes  of 
the  earth,  mull,  notwithstanding,  in  fome  of  them, 
be  denied  the  ufe  of  fuch  aliments  as  nature  had 
rendered  effentially  neceffary  to  the  continuation 
of  his  exigence, 

§  342. 
Of  all  animals,  wi:h  which  we  are  in  any  mea- 
fure  acquainted,  man  may,  with  the  ft r i 61  e ft  pro- 
priety and  truth,  be  faid  to  be  omnivorous.  As 
on  the  one  hand  he  is  calculated  to  banquet  in 
luxury,  amidfl  the  mod  profufe  variety  of  delica- 
cies that  aft  can  prepare  from  the  immenfe  re- 
fources  of  the  animal  and  vegetable  kingdoms, 
fo,  on  the  contrary,  he  is  able  to  retain  his  health 
•and  vigour  when  fubfifling  on  the  moft  fimple  and 
frugal  fare. 

Thus,  to  produce  only  a  very  few  examples,  a 
great  many  men  even  at  the  prefent  day  fubfift 
folely  on  a  vegetable  diet,  fuch  as  potatoes,  chef- 
nuts,  dates,  &c.  which  confHtuted  alfo  the  food  of 
the  firft  progenitors  of  the  human  race  :  for  it  ap- 
pears highly  probable,  that  thofe  fimple  and  hardy 
fops  of  nature,  fupported  life  firft  by  the  fruits  and 

roots 


OF  FOOD  AND  APPETITE.  7 

roots  of  plants,  and  afterwards,  by  the  more  fub- 
flantial  and  durable  fare  of  grains  and  pulfe. 

Some  of  the  Moorifh  tribes  in  Africa  live  aimed 
entirely  on  the  gum  fenegal. 

The  inhabitants  of  Kamfchatka  and  of  a  great 
many  other  maritime  fituations  fubfift  on  fifh. 

In  Europe  itfelf,  the  Morlachi  are  fupported  al- 
mofl  entirely  on  a  diet  of  flefli. 

Some  nations  of  Barbarians  fubfift  even  on  raw 
HeMi,  a  circumttance  which  is  undoubtedly  true, 
with  refpect  to  the  Samoids,  the  Efquimaux,  and 
certain  tribes  of  people  inhabiting  South  America. 

Neither  are  the  liquids  made  ufe  of  as  drinks, 
in  certain  nations,  lefs  lingular  and  (biking. 

Thus  the  inhabitants  of  fcveral  iflands,  which 
lie  between  the  tropics,  more  efpecially  thofe  fitu- 
ated  in  the  Pacific  Ocean,  arc  entirely  deftitute  of 
fvveet  and  pleafant  water,  and  therefore,  as  a  fub- 
ftitute  for  this  fluid,  ufe  the  delicious  juice  of  the 
I  a  clef  cent  cocoa. 

Others   again  drink  the  waters  of  the  briny 

ocean  ; — from  all  which  fa£h  and  circumftances, 

A  4  taken 


S  OF  MASTICATION 

taken  colle&ively,  together  with  an  infinitude  of 
others  that  might  be  adduced,  we  need  not  hefitate 
a  moment  to  pronounce,  that  man  is  literally  an 
omnivorous  animal. 


SECT.    XXVII. 
OF  MASTICATION  AND  DEGLUTITION. 

§  343- 

-TOR  the  purpofe  of  maflicating  the 
more  folid  fpecies  of  food,  both  our  under,  and 
upper  jaws,  are  armed  with  three  different  kinds 
of  teeth. 

Thefe  are  firfl,  the  incifores,  which,  in  moil: 
men,  are  chifel-formed,  and  well  calculated  to  bite 
off  morfels  of  food. 

Secondly,  the  canini,  ftrong,  conical  and  com- 
pletely adapted  for  breaking  fubftances  of  greater 
iirmnefs. 

.And  la/lly,  the  molares,  of  different  fizes,  exqui- 
fkely  fitted  for  the  procefs  of  grinding. 

§  344- 


AND  DEGLUTITION.  9 

§  344- 

The  mandible  or  lower  jaw  is  connected  to  the 
other  parts  of  the  head,  by  means  of  a  very  lingu- 
lar variety  of  articulation,  which  appears  to  be  of 
a  middle  nature  between  arthroida  and  ganglimus. 
Being  furnifhed  with  a  pair  of  double  concave  car- 
tilages, it  thus  unites,  to  a  fufficient  degree  of 
flrength  and  firmncfs,  a  capacity  of  being  eafily 
and  very  confiderably  moved  in  all  directions. 

The  under  jaw  is  drawn  back,  in  opening  the 
mouth,  chiefly  by  means  of  the  miifculu?  bivente?-, 
but  in  part  alfo  by  the  geniohyoidei  and  the  my- 
lohyoidei. 

It  is  brought  back  again,  when  we  attempt  to 
cut  any  thing  through  with  the  dentes  incifores, 
and  prefled  with  aftonifhing  force  againfr.  the 
oppofite  jaw,  during  our  efforts  to  crufh  any 
hard  fubftances,  by  the  maffeter  and  temporal 
mufcles. 

It  is  moved  laterally  in  chewing,  by  the  action 
of  the  internal  and  external  pterygoid  mufcles ; 
the  latter  of  which  have  alfo  the  power  of  moving 
it  in  a  forward  direction. 

§  345- 


10  OF  MASTICATION 

§  345- 
Subftances  taken  into  the  mouth  for  the  pur- 

pofe  of  being  chewed,  are  retained,  placed  in  a 

proper  fituation,  and  thus  effectually  fubjected  to 

the  action  of  the  teeth,  by  means  of  the  mufculus 

buccinator )  and  the  tongue,  an  organ  of  extreme 

flexibility,  and  very  capable  of  changing  its  form 

(S  233> 

§  34& 
During  the  act  of  manducation  we  emulge,  as 
it  were,  a  certain  quantity  of  faliva,  which  is  an 
aqueous  liquid,  of  a  nature  fomewhat  faponace- 
ous  ;  it  contains  a  fmall  quantity  of  earthy  matter, 
(which  gives  origin  to  tartarous  incruftarions  of 
the  teeth,  and  to  fmall  fublingual  calculi) ;  this 
fluid,  from  being  in  perpetual  contact  with  the 
tongue,  mafccs  no  fenfible  impreflions  of  tafte  on 
that  organ,  although  it  contains  a  fmall  quantity 
of  microcofmic  fait ;  it  poffefles  antifeptic  and  re- 
folvent  properties,  and  has  alfo  a  power  of  fpee- 
dily  exciting  the  procefs  of  fermentation  in  vege- 
table fubftances,  efpecially  in  thofe  of  the  farina- 
ceous kind. 

§  347- 
The  fources  from  whence  this  fluid  is  derived 
are,  fmall  conglomerate  glands,   cf  three  feveral 

orders, 


AND  DEGLUTITION.  n 

orders,  the  lateral  and  internal,  of  which  are  fitu- 
ated  beneath  the  lower  jaw. 

The  mod  confulerable  of  thefe  glands,  called 
parotids,  (remarkable,  on  account  of  being  ex- 
tremely fubject  to  metaftafes),  excrete  their  faliva 
through  the  Stenonian  duct,  juft  behind  the  middle 
molar  tooth  of  the  upper  jaw. 

The  faliva  furnifhed  by  ihc/ubmaxUlary  glands., 
is  difcharged  through  the  duel:  of  Wharton. 

That  derived  from  the  fublingual  glands,  which 
are  the  lead  of  all,  flows  through  the  numerous 
ducts  of  Rivinus. 

s  348- 

The  excretion  of  faliva,  (of  which,  in  confor- 
mity to  the  opinion  of  Nuck,  about  a  pint  is  com- 
monly fuppofed  to  be  fecreted  in  the  fpace  of 
twelve  hours),  is  confiderably  encreafed  both  by 
the  application  of  any  ftimulating  fubftance,  and 
alfo  by  mechanical  prefTure,  the  latter  of  which 
appears  to  aft  merely  by  emulging  the  containing 
parts. 

Thus,  whatever  hard  fubftances  we  chew,  be- 
come perfectly  moiflened  and  macerated,  as  it 
were,  by  a  copious  afflux  of  faliva  produced  in 

confe- 


12  OF  MASTICATION 

confequence  of  the  prcflure,  to  which  the  parotids 
are  particularly  expofed  from,  being  fituated  fo 
near  to  the  articulation  of  the  lower  jaw. 

With  regard  to  the  operation  of  flimuli  on  the 
fecretion  of  this  fluid,  it  is  neceffary  farther  to  ob- 
ferve,  that  when  acrid  fubftances  are  taken  into 
the  mouth,  a  plentiful  afflux  of  faliva  is  immedi- 
ately produced,  which  has  the  effect  of  diluting 
and  thus  effectually  counteracting  the  irritating 
acrimony  :  an  increafe  of  the  fame  fluid  is  alfo  oc- 
cafionally  produced  by  the  flimulus  of  the  imagi- 
nation ;  to  this  caufe  muft  wc  refer  that  afflux  of 
faliva,  which  fo  frequently  accompanies  a  itrong 
appetite  for  food. 

§  349- 
With  the  faliva  are  blended  a  fine  aqueous, 
dew-like  fluid,  which  tranfudes  from  the  foft  parts 
of  the  mouth,  and  alfo  a  mucus,  fecreted  by  fmall 
glands,  fituated  in  the  lips  and  cheeks :  it  is  a 
portion  of  this  mucus  by  which  the  tongue  is  lu- 
bricated. 

§   35°- 
The  morfel  during  maftication,  being  thorough- 
ly moiftened  by  this  mixture  of  faliva  and  other 
animal  juices,  is  thus,  not  only  converted  by  de- 
grees into  a  foft  pulpy  bolus,  more  fit  for  the  pur- 

pofc 


AND  DEGLUTITION.  13 

pofe  of  deglutition,  but  is  likewife  prepared,  at 
the  fame  time,  for  further  digeflion  and  final  affi- 
milation. 

§  351- 

The  adtual  bufinefs  of  deglutition,  although  it 
appears  to  be  of  a  very  compound  nature,  and  is 
indeed  performed  by  the  co-operation  of  a  great 
many  different  parts,  may  be  confidered  as  com- 
mencing and  proceeding  in  the  following  order  ; 
viz.  the  tongue  being  firft  retracted  towards  its 
bafis,  and  becoming  therefore  fomewhat  turgid 
and  ftiff,  receives  on  its  excavated  dorfum  or  back, 
the  lubricated  and  moiftened  bolus,  which  is  from 
thence  forced  onwards  into  the  fauces,  where  it 
is  received  by  the  expanded  infundibulum  of  the 
■pharynx ,  which  appears,  at  the  fame  time,  to  ad- 
vance fomewhat  upwards  ;  on  the  reception  of  the 
food  the  infundibulum  makes  a  Angular  and  vio-. 
lent  exertion,  which  may  be  fuppofed  to  proceed 
from  a  fpecies  of  vita  propria  ;  from  this  funnel- 
like entrance,  the  bolus  is  again  protruded  on- 
ward, by  a  threefold  contraction  of  the  pharynx, 
into  the  cefophagus.  All  the  above  motions  fuc- 
ceed  each  other  with  the  utmoft  degree  of  rapidi- 
ty, and  are  of  extremely  fhort  continuance. 

§   352- 
For  the  purpofes  of  expanding  this  paiTage,  and 

rendering  it  at  the  fame  time  Heady  and  fecure, 

nature 


14  OF  MASTICATION 

nature  has  made  the  mod  ample  provifion  by  a 
variety  of  auxiliary  parts. 

The  motion  of  the  tongue,  in  this  momentous 
bufinefs,  is  regulated  and  directed  by  the  os  hyo- 
ideum. 

To  prevent  any  of  the  fubftances  fwallowed, 
from  palling,  by  miftake,  either  into  the  internal 
nares,  or  into  the  euftachean  tubes,  the  foft  palate 
is  very  wifely  provided.  This  flcfhy  curtain,  de- 
pending equally  from  the  arched  roof  to  which  it 
is  attached,  is  capable  of  being  rendered  tenfe  by 
the  action  of  a  peculiar  fet  of  mufcles,  and  thus 
the  above  pafTages  may  be  completely  clofed. 

The  glottis  is  fecurely  guarded  by  the  tongue 
itfelf,  becaufe  at  the  very  inftant  in  which  we  at- 
tempt to  fwallow,  the  larynx,  being  drawn  up- 
ward and  forward,  is  in  a  certain  degree  concealed 
beneath  the  retracted  bafis  of  the  tongue,  and  is 
fo  compreffed  by  it,  that  the  glottis,  not  only  by 
this  conftriction,  but  alfo  by  the  additional  fecurity 
of  the  epiglottis,  is  thus  very  effectually  guarded 
againft  the  intrufive  entrance  of  any  heterogene- 
ous fubftances. 

§  353- 
Finally,  the  bufinefs  of  deglutition  is  greatly  fa- 
cilitated by  means  of  a  quantity  of  mucus,  with 

which 


AND  DEGLUTITION.  15 

"which  the  whole  of  the  paffage  above  defcribed 
is  lubricated ;  and  which,  befides  the  lingual 
glands  already  mentioned  (§  235),  is  chiefly  fur- 
nifhed  by  the  numerous  finufes  of  the  tonfils,  and 
by  that  infinitude  of  mucaginous  cryptKi  fo  pro- 
fufely  beftowed  on  the  larynx  itfelf. 

§  354- 

"Wiih  refpeft  to  the  ccfophagas  itfelf,  through 
which  all  fubftances  fwallowed  muft  neceffarily 
pafs,  previoufly  to  their  entrance  into  the  fiomach, 
it  is  a  flefhy  canal,  rather  narrow  in  its  diameter, 
and  exceedingly  firm  and  flrong,  but  at  the  fame 
time  pliable,  di!atable,and  poffeffed  of  a  high  degree 
cf  ferifibility :  it  is  compofed  of  tunics  or  coats, 
which,  if  we  except  the  difference  in  their  thick- 
ntfs,  bear  no  fmall  refcmblance  to  the  coats  of  the 
other  portions  of  the  alimentary  canal. 

Thus,  the  external  covering  is  mufcular,  made 
up  of  fibres  running  both  longitudinally  and  in 
tranfverfe  or  circular  directions. 

The  middle  coat  is  nervous,  ending  on  each  fide 
in  a  very  lax  cellular  membrane,  by  means  of 
which  it  is  connected,  as  well  to  the  preceding,  as 
to  the  fubfequent  tunic. 

Laflly, 


itf  OF  DIGESTION. 

Laftly,  the  internal  coat  is  lined  by  mucus  of  an 
exquifite  degree  of  lubricity. 

§  355- 

The  following  appears  to  be  the  mode  in  which 
this  canal  performs  its  office  ;  as  foon  as  it  has  re- 
ceived either  a  draught  or  bolus  completely  within 
its  parietesy  the  parts  immediately  above  prefently 
contraft  themfelves,  thus  forcing  downwards  the 
fubftance  to  be  fwallowed  ;  which,  if  it  be  a  bo- 
lus, can  be  protruded  onward  only  by  one  uni- 
form feries  of  exertions  in  the  furrounding  tube, 
till  it  has  palTed  through  the  diaphragm,  and  been 
finally  received  into  the  cavity  of  the  ftomach 
itfelf. 


SECT.    XXVIII. 

OF  DIGESTION. 

1  HE  chamber,  or  immediate  feat  of  di- 
geftion,  is  the  ftomach ,  a  vifcus  more  uniformly 
pofTefled  than  any  other,  by  almoft  every  indivi- 
dual throughout  the  immenfe  range  of  animated 
nature :  if,  therefore,  we  eftimate  the  dignity  of 
the  feveral  vifcera  from  this  circumftance  alone, 
the  ftomach  is,  dcubtlefs,  to  be  confidered  as  an 

i  organ 


OF  DIGESTION.  17 

crgan  furpaffing  all  the  others  in  utility  and  im- 
portance to  the  animal  economy. 

§  357- 
The  human  flomach  refembles  a  leathern  pouch, 

of  very  confiderable  dimenfions,  fufficient,  for  the 

mod  part,   in  an  adult,  to  contain  three  pints,  or 

more,  of  water,  and  furnifhed  with  two  feparate 

orifices  or  mouths  : 

Thefe  are,  fir/},  a  fuperior  orifice,  called  car- 
dia,  which  is  formed  in  the  place  where  the  cefo- 
phagus,  by  a  plaited  and  fomewhat  oblique  aper- 
ture, opens  into  the  flomach  itfelf,  and  points  to- 
wards the  bottom  of  this  vifcus,  or  that  extremity 
which  regards  the  left  fide  of  the  body. 

Secondly,  an  inferior  one,  which  conflitutes  the 
termination  of  the  right,  and  lefs  capacious  end  of 
the  flomach  :  this  orifice  is  called  pylorus^  and  de- 
fcends  a  fliort  diftance  into  the  cavity  of  the  ad- 
joining duodenum. 

§  353. 

The  fituation  of  the  flomach,  when  empty,  is 
different  from  that  of  the  fame  organ,  when  full : 
thus,  in  the  former  ftate,  it  hangs  loofe  and  flaccid 
in  the  abdominal  cavity,  in  fuch  a  manner  that  its 
greater  curvature  looks  in  a  backward  direction  -9 

vol.  11.  B  and 


1 8  OF  DIGESTION. 

and  its  pylorus,  being  turned  fomewhat  upwards-, 
forms  a  plaited  or  twifted  angle  with  the  duode- 
num, to  which  it  is  connected. 

But  in  the  latter  ftate,  when  diftended  with  food, 
its  greater  curvature  is  again  turnrd.  and  looks  in 
an  anterior  direction,  fo  that  the  tj  lorus  enters 
now,  by  a  more  direct  route,  into  the  duodenum  ; 
whereas  the  cardia,  on  the  contrary,  is  fo  folded 
and  bent  as  to  be  completely  clofed, 

§   359- 
The  ftomach    is   compofed    of   four   principal 
coats,  diftinguifhed  and  feparated  by  three  others, 
of  an  entirely  cellular  nature,  which  lie  between 
them. 

The  mod  external  of  thefe  coverings  is  common 
to  the  ftomach,  with  all  the  reft  (fave  a  fmall  por- 
tion) of  the  alimentary  canal,  and  is  continued 
over  the  omenta,  which  fliall  be  fpoken  of  here- 
after. 

Next  to  this,  lies  that  cellulo-mufcular  coat,  (o 
very  ftriking  in  irs  nature  and  properties,  on  which 
depend  both  the  exquifite  irritability  of  the  fto- 
mach (§  306.),  and  alfo  its  periftaltic  motion  ;  the 
latter  of  which  fliall  be  a  fubject  of  confideration 
in  another  place.  This  coat  is  compofed  of  dif- 
ferent 


OF  DIGESTION.  t$ 

ferent  ftrata  of  mufcular  fibres,  which  are  ufually 
divided  into  three  orders,  one  longitudinal,  and 
two  circular  ;  the  circular  fibres  are  again  divided 
into  thofe  that  are  dtreclly*  and  thofe  that  are  ob- 
liquely, circular.  It  mud,  however,  be  obferved, 
that  fo  extremely  variable  and  irregular  are  the  fi- 
bres of  this  coat,  with  regard  to  their  direction 
and  diftribution,  as  fcarcely  to  admit  of  reduction 
to,  and  arrangement  under,  any  determinate  and 
general  rules. 

The  third  principal  coat  is  called  the  nervous, 
an  appellation  extremely  improper,  as  it  is  compo- 
fed  wholly  of  condenfed  cellular  membrane,  be- 
coming gradually  more  foft  and  lax  on  each  fide ; 
by  which  means  it  is  connected  externally  to  the 
mufcular,  and  internally  to  what  we  (hall  prefently 
call  the  villous,  coat.  It  is,  notwithstanding,  fo 
firm  and  robu(t,  that  it  may  be  aptly  enough  call- 
ed the  bafts  of  the  whole  flomach. 

Laftly,  the  internal  coat,  which  has  been  very 
improperly  called  vil'ous,  ii  exceedingly  tender, 
fomewhat  fpongy,  porous,  and  folded  into  a  very 
great  number  of  rugce  or  wrinkles,  fo  that  its  area 
is  much  more  extenfive  than  that  of  any  of  the 
other  coats  which  we  have  juft  defcribed  :  it  every 
where  exhibits  cells  cf  the  utmoft  minutenefs,fome- 
B  2  what 


20  OF  DIGESTION. 

what  fimilar  in  appearance  to  thofe  larger  ones, 
with  which  the  reticulum  of  ruminating  animals 
is  very  beautifully  and  elegantly  characterized. 

The  internal  furface  of  this  coat  is  lined  with 
mucus,  apparently  fecreted  by  fmall  mucaginous 
cryptse,  fome  of  which  may  be,  indeed,  readily 
enough  diftinguifhed  near  to  the  pylorus,  or  lower 
orifice  of  this  organ. 

§   36°- 
The  flomach  is  furnifhed  with  an  aflonifliing 

apparatus  of  nerves,  whence  its  fenfibility  is  fo  ex- 
quifite,  that  it  is  capable  of  being  very  readily  af- 
fected by  flimuli  of  almoft  every  kind,  whether 
they  be  external,  as  cold  &c.  or  internal  as  food, 
and  even  by  the  inquiline  humours  themfelves. 
From  the  fame  fource  arifes  alfo  that  exteniive, 
and  truly  admirable  confent,  which  exifls  between 
this  important  vifcus  and  mofl  of  the  other  func- 
tions of  the  body;  to  which  head  belongs,  in  a 
particular  manner,  the  flriking  effects,  produced 
on  the  flomach,  by  all  mental  commotions,  and 
alfo,  on  the  other  hand,  the  very  powerful  influ- 
ence of  an  entirely  found  and  healthy  flate  of  this 
organ,  on  the  cheerfulnefs  and  ferenity  of  the 
mind, 

§  56i. 


OF  DIGESTION.  2i 

§  56l. 

The  number  and  functions  of  the  blsod  vejfels, 
belonging  to  the  ftomach,  are  no  lefs  confiderable 
and  ftriking,  than  thofe  of  the  nerves.  The  fmall 
arteries,  (of  which  an  infinitude  of  different  or- 
ders, are  minutely  interfperfed  throughout  the  cel- 
lular coats  of  this  organ),  appear  to  conftitute  the 
immediate  fources  of  the  gqfiric  juice,  a  liquor 
which  flows  in  perpetual  ftreamlets  from  the  inter- 
nal furface  of  the  ftomach. 

§  362- 

This  juice  bears,  on  the  whole,  no  fmall  refem- 
blance  to  faliva,  except  that,  agreeably  to  the  ex- 
periments of  the  illuftrious  Spalanzani,  its  powers 
are  counter  to  thofe  which  promote  fermentation. 
As  to  the  reft  of  its  properties,  it  is  faponaceous, 
equally  antifeptic  with  the  faliva,  and  is  indeed,  a 
very  powerful  menftr-uum,  fuflicient  gradually  to 
dhTolve  milk  after  it  has  been  gently  coagulated  in 
the  ftomach. 

§  363- 
The  gaftric  juice  appears  to  be  the  moft  power- 
ful and  active  agent  in  the  great  bufmefs  of  digef- 
tion.  If  the  food  be  carefully  mafticated,  and  fuf- 
ficiently  blended  with  the  menftruum  furnifhed  by 
the  falivary  glands,  this  fluid  of  the  ftomach  com- 
B  3  pletely 


12  OF  DIGESTION. 

pletely  difTolves,  and  finally  converts  it,  into   a 
foft  pultaceous  chyme. 

§  364" 
This  momentous  function  is  alfo  further  aided 
and  promoted,  by  a  variety  of  acceflbry  and  afiif- 
tant  powers  :  of  thcfe  the  molt  considerable  is  the 
feriftaltic  motion,  by  means  of  which  the  food, 
now  reduced  to  a  pulpy  confidence,  is  thoroughly 
agitated,  and  kept  perpetually  in  a  ftate  of  wavy 
commotion.  Although  the  force  of  the  periftaltic 
motion  fall  far  {hort  of  the  chimerical  calculations, 
formerly  made  on  this  fubjeft,  by  mathematical 
phyficians,  and  although  it  be  not  itlelf  the  fole 
caufe  of  digeftion,  it  is,  notwithstanding,  of  the 
utmofl;  efficacy  and  influence  in  this  important 
procefs. 

§   365- 

Among  the  auxiliary  powers,  of  this  kind,  may 
be  alfo  reckoned  another  fpecks  of  motion,  which 
the  preflure  of  the  furrounding  parietes  of  the  ab- 
domen, communicates  to  the  ftomach  :  to  thefe 
we  may  flill  farther  fubjoin,  the  extreme  warmth 
of  the  fituation  in  which  this  vifcus  is  placed ;  fo 
very  powerful  was  this  fotus  or  bath,  formerly 
efteemed,  in  confequence  of  the  abundant  quan- 
tity of  blood  contained  in  the  neighbouring  vefifels 

and 


OK  DIGESTION.  23 

and  vifcera,  that  inftead  of  the  term  digejiion, 
that  of  coclion,  was  ufed  by  the  greater  part  of 
phyfiologifls. 

§  366- 
To  determine,  with  precifion,  the  period  of  time 
requifite  for  the  converfiofi  of  our  aliment  into 
chyme  by  the  joint  co-operation  of  the  foregoing 
powers  (§  361.),  will  appear  almofl:  impoffible  to 
any  one,  who  may  c  mfider  the  great  variety  of 
ciroimftances,  on  which  fuch  converlion  mud  de- 
pend :  thefe  circumflances  are,  the  quality  and 
quantity  of  the  food  taken  in,  the  different  degrees 
of  force  in  the  digeftive  powers,  the  greater  or 
lefs  attention  and  care  bellowed  on  the  prepara- 
tion of  the  food  for  digeftion,  by  previous  rnafti- 
cation,  &c. 

For  in  a  healthy  fubjec~t,  the  unimpaired  fto- 
mach  does  not  difcharge  fuch  alimentary  matters 
as  have  been  taken  in,  previouily  to  the  conver- 
fion  of  their  digeftible  parts  into  a  perfect  pulp. 
From  whence  it  is  evident,  that  different  periods 
of  time  are  requifite,  for  the  complete  digeflion  of 
different  kinds  of  food.  If,  however,  it  be  allow- 
able to  form  any  general  conclufion  on  this  fubjec'r, 
it  would  appear,  that  from  the  third,  to  the  fixth 
hour,  after  the  ufe  of  aliment,  the  flomach  has, 
for  the  mofl  part,  difcharged  through  the  pylorus, 
B  a  ia 


44  OF  DIGESTION. 

in  a  very  gradual  manner,  the  whole  of  its  pul- 
taceous  contents. 

§  36> 
The  pylorus  is  an  annular  rim,  not  formed, 
(like  the  other  rugce  on  the  internal  furface  of  the 
flomach),  by  the  folding  of  the  villous  coat  alone, 
but  confuting,  in  part,  alfo  of  a  few  fafciculi  from 
the  fubjacent  nervous^  and  alfo  of  certain  fibres 
from  the  mufcular^  coat :  all  which  parts  are  fo 
organized  and  arranged,  as  to  conflitute  a  coniform 
termination  to  the  flomach,  that  is  extended  into, 
and  embraced  by,  the  duodenum,  in  the  fame 
manner  as  the  os  uteri  is  received  and  embraced, 
by  the  fuperior  part  of  the  vagina. 


SECT.    XXIX. 

OF  THE  PANCREATIC  JUICE. 
§     368. 

Subsequent  to  the expuhion  of 

the  chyme  through  the  pylorus,  that  pulpy  mafs 
mud  be  fubje&ed,  in  the  duodenum  (a  fhort,  but 
remarkable  portion  of  the  inteftina!  tube),  to  new 
and  confiderable  changes,  previoufly  to  the  for- 
mation 


OF  THE  PANCREATIC  JUICE.  25 

mation  and  final  reparation  of  complete,  alimen- 
tary chyle.  Thefe  neceffary  changes  are  effe&ed 
in  the  chyme  by  the  acceffion  and  admixture  or 
various  kinds  of  inquiline  humours,  the  mod  (hik- 
ing and  important  of  which,  are,  the  bile  and  the 
pancreatic  juice. 

§  369- 
Of  thefe  two  humours,  we  will  fpeak  in  fepa- 
rate  fec"Hons.  We  proceed  therefore,  to  confider 
the  liquor  of  the  pancreas  firft,  becaufe  it  appears 
to  bear  a  very  confiderable  refemblance,  both  in 
its  nature  and  ufes,  to  thofe  other  two  diffolvent 
humours,  of  which  we  have  already  fpoken,  name- 
ly, the  faliva  and  the  gaftric  fluid. 

§  37°- 
Athough  it  be  indeed  a  matter  of  no  fmall  diffi- 
culty, to  procure  the  pancreatic  liquor  of  a  found 
animal,  in  a  pure  and  unadulterated  date,  yet  the 
obvious  and  unequivocal  refult  of  all  the  fa£b, 
which  the  moft:  attentive  investigation  has  been 
able  to  fupply,  with  regard  to  its  nature,  is,  that 
it  bears  the  itrongeft  fimilitude  to  the  faliva  in  all 
its  general  properties.  Were  it  not  for  the  pur- 
pofe  of  fhowing  how  mifchievous,  and  even  de- 
finitive, the  practice  of  medicine  may  become, 
unlefs  directed  by  found  principles  of  -V  .logy, 
I  fhould  not  think  it  neceffary  nor  ev         uper,  at 

the 


x6  OF  THE  PANCREATIC  JUICE. 

the  prefent  enlightened  period,  to  mention  the  er- 
roneous phyfiological  hypothefes,  entertained  by 
Franc.  Sylvius,  and  his  humble  followers,  Regn. 
de  Graef,  Flor.  Schuyl,  and  others,  refpedting 
the  vifionary  or  fuppofed  acidity  of  the  pancreatic 
liquor,  efpecially  as  thofe  opinions  have  been  long 
fince  very  ably  refuted  by  Pechlin,  Swammerdam, 
and  Brunner,  characters  of  the  firft  celebrity  in 
the  annals  of  medical  fcience. 

§  371- 

The  fources  from  whence  the  lymph  and  faliva 
are  derived,  bear  no  fmall  refemblance  to  that 
which  constitutes  the  fubject  of  our  prefent  confi- 
deration,  namely,  the  pancreas  :  this  latter  is  by 
far  the  largefl  of  all  the  conglomerate  glands  of 
the  human  body,  and  exhibits,  in  the  whole  of  its 
ftruclure,  a  very  flriking  fimilitude  to  the  glands, 
that  give  birth  to  the  falivary  fluid ;  with  thefc 
laft  mentioned  bodies  it  alfo  further  agrees,  in  this 
particular,  that  its  excretory  canals,  arifing  from 
radicles  of  the  utmoli  minutenefs,  run  together 
and  unite  by  degrees,  till  they  conftitute  finally  a 
common  duct,  which  has  received  its  name  from 
Jo.  G.  Wirfung,  who  firfl:  difcovered  and  de- 
monstrated it  in  the  human  fubject,  in  the  year 
1642. 

This 


OF  THE  PANCREATIC  JUICE.  27 

This  duel:  paffes  through  the  coats  of  the  duo- 
denum, and  by  a  conflant  Jlillicidium,  weeps  into 
the  cavity  of  that  inteftine,  the  fluid  it  had  receiv- 
ed from  the  gland  to  which  it  is  appended. 

§   372' 

Finally,  the  excretion  of  this  fluid  appears  to  be 
promoted  by  the  very  fame  powers,  which  were 
formerly  faid  to  be  fubfervient  to  the  excretion  of 
faliva,  namely,  prejjiire  zi\djiimulus. 

By  means  of  the  former,  it  is  emulged  chiefly 
when  the  ftomach  is  diftended  and  reds  immedi- 
ately on  the  pancreas. 

The  fubftances  that  contribute  moft,  by  their 
irritations,  to  excite  a  difcharge  of  the  pancreatic 
fluid  are,  firft,  the  chyme  irfelf,  as  it  paffes  through 
the  pylorus  in  a  crude  and  unaflimilated  (late  ;  and 
fecondly,  the  bile,  which  is  difcharged  through 
the  very  fame  orifice  with  the  liquor  of  the  pan- 
creas. 

§  373- 

The  ufe  of  this  fluid  is  doubtlefs  to  diflblve  the 
chyme,  more  efpecially  that  part  of  it,  which  has 
not  been  fufficiently  digefted  in  the  ftomach  :  by 
its  abundant  afflux,  it  contributes  to  aflimilate  this 

pulpy 


2  8  OF  THE  BILE. 

pulpy  mafs  ft  ill  more  and  more  to  the  nature  of 
the  inquiline  humours,  and  thus  finally  mature  it 
for  the  further  procefs  of  chylification. 


SECT.    XXX. 
OF    THE    B  I L  E  ». 


§  374- 


T 


H  E  fecretion  of  bile  is  the  pecu- 
liar deftination  of  the  liver,  the  largeft  and  moil 
ponderous  vifcus  in  man.  This  fuperiority  of  fize 
is  more  especially  obfervable,   during  the  fcetal 

*  Dottor  Maclurg,  of  Virginia,  publifhed  in  the  year 
1772,  an  experimental  treatife  on  the  formation,  the  nature 
and  the  ufes  of  the  human  bile,  which  has  acquired  for  its 
learned  and  ingenious  author,  no  fmall  degree  of  reputation 
both  at  home  and  abroad.  That  this  elaborate  publication 
pofleffes  an  uncommon  fliare  of  merit,  not  even  the  avowed 
enemies  of  the  DocTor  are  themfelves  able  to  deny.  The 
author  has  fliewn  himfelf  to  be,  at  lead,  a  very  patient  expe- 
rimenter, and  an  extremely  attentive  obferver.  He  appears 
to  have  made  himfelf  perfectly  matter  of  the  opinions  of  all 
authors  of  celebrity  and  diftindion,  who  had  previoufly  writ- 
ten on  the  fame  fubjecl.  With  regard  to  the  literary  merit  of 
the  compofition  itfelf,  it  is  doubtlefs  entitled  to  die  higheft  en- 
comiums that  even  the  moil  partial  eulogift  can  beftow.   The 

order 


OF  THE  BILE.  29 

fhte,  in  which,  the  younger  the  foetus  the  greater 
is  the  proportional  magnitude  of  the  liver,  when 
compared  with  that  of  the  other  vifcera  of  the 


order  is  inimitably  lucid,  the  ftyle  is  chafte,  manly  and  ner- 
vous in  the  higheft  degree,  and  as  to  clofenefs  and  propriety 
of  argumentative  arrangement,  not  even  the  fupercilious  lo- 
gician himfelf,  can  find  room  to  fugged  the  fhadow  of  an 
amendment. 

All  human  compofitions  are,  however,  like  the  fources 
from  whence  they  originate,  in  fome  meafure  faulty  and  im- 
perfect. To  this  general  maxim,  humiliating  as  it  may  ap- 
pear to  the  pride  of  the  felf-adoring  philofopher,  the  treatife 
of  the  illuftrious  Maclurg  is  by  no  means  an  exception.  In 
feveral  of  the  Doctor's  experiments  there  appears  to  be  a 
want  of  fufficient  accuracy  and  definitude,  in  others  a  want 
of  object  and  defign.  Over  thefe  faults,  however,  confider- 
able  as  they  are  in  the  works  of  an  experimentalift,  we  feel 
inclined  to  fpread  a  kind  mantle  of  palliation,  when  we  re- 
collect that  our  author  experimented  and  wrote  in  the  early 
morn  of  fcientific  chemiftry.  Experimenters  had  not  yet  be- 
come perfect  adepts  in  their  nice  and  momentous  art ;  they 
had  not  yet  acquired  fafficient  circumfpection  and  addrefs  to 
obviate  every  fource  of  fallacy,  and  to  avail  themfelves  of 
every  circumftance  that  might  pave  the  way  to  fatisfactory 
and  unequivocal  refults. 

But  another  charge  of  a  more  weighty  and  important  na- 
ture, lies  againft  our  learned  and  ingenious  author.  He  has 
certainly  built,  on  nothing  more  fubftantial  than  the  flimfy 
bails  of  deceptious  analogy,  fome  of  the  leading  principles  ot 
his  favourite  doctrine.     Thus,  for  example,  he  fuppofes  the 

bile 


30  OF  THE  BILE. 

body.  The  dignity  and  high  importance  of  this 
vifcus  in  the  animal  economy  may  be  fairly  de- 
duced, from  the  univerfality  of  its  prefence  ;  thus 

bile  to  be  a  fluid,  the  direct  refult  of  a  putrefactive  degene- 
racy in  a  portion  of  the  circulating  volume  of  the  blood. 
His  moft  plaufible  reafons  in  fupportof  this  opinion  a.re,J;r/l, 
that  the  parts,  from  whence  the  incipient  radicles  of  the  vena 
portarum  immediately  originate,  contain,  and  communicate 
with,  matter  already  in  a  femiputrefcent  ftate.  And  ficond- 
ly>  that  the  bile  is  moft  abundant  in  quantity  and  moft  active 
with  regard  to  its  quality,  at  that  feafon,  and  under  thofe 
circumftances,  which  arc  moft  favourable  to  the  commence- 
ment and  progrefs  of  putrefaction  in  the  living  fytlem,  a? 
well  as  in  all  other  phyfical  bodies. 

Plaufible  as  thofe  arguments  may,  on  firft  view  appear, 
they  are  certainly,  as  already  obferved,  founded  on  nothing 
better  than  fair,  but  fallacious  analogy.  The  principle 
which  they  tend  to  efiablifh  ftands  in  the  moft  direct  opposi- 
tion to  the  refult  of  experiment — facred  experiment !  the  on- 
ly unerring  guide  to  conduft  the  candid  enquirer  to  the  erer- 
lafting  temple  of  truth.  Did  our  learned  author  (I  would 
beg  leave  to  afk)  ever  faithfully  experiment  on  feparate  por- 
tions of  the  blo^d,  drawn  from  different  parts  of  the  body,  in 
order  to  determine  the  comparative  proximity  of  each  portion, 
to  the  putrefactive  Mate  ?  I  prefume  he  never  did,  otherwife 
his  opinion  on  this  fuhject  would  have  been,  dcubtlefs,  very 
different  from  what  we  find  in  his  ingenious  publication. 
For  it  is  a  truth,  nothing  the  lefs  facred  and  refpectable  on 
account  of  its  novelty,  that  if  equal  quantities  of  blood  be 
taken  from  the  venapcrtarum,  and  from  the  lungs  or  any  part 
of  the  arterial  fyftem,  and  expofed  to  the  fame  incumbent 

circum- 


OF  THE  BILE.  32 

in  all  animals  poiTeffing  red  blood,  it  exifts  no  lefs 
generally  and  uniformly  than  the  heart  itfelf. 

circumftances,  the  pulmonic  or  arterial,  will  affume  the  putre- 
factive procefs,  much  fooner  than  the  hepatic,  blood.  The 
caufe  of  this  phenomenon  muft  be  rifKciently  obvious  to  any- 
one acquainted  with  the  late  dilLoveries,  in  the  divine  fciencc 
of  chemiftry.  We  would  attempt  its  folution  in  the  follow- 
ing manner. 

Vital  air  (which  is  indeed  the  genuine  feptic  principle,  if 
any  fuch  principle  exift)  is  in  all  cafes  e/Tential  to  the  progrefs 
of  putrefaction.  This  air,  or  rather  its  bafe  (termed  oxygene 
by  the  ingenious  chemifts  of  France)  is,  as  we  have  the  firong- 
eft  reafons  to  believe,  from  the  experiments  cf  Goodwyn, 
Beddoes,  Girtanner,  and  others,  intimately  blended  with  the 
circulating  blood  in  its  paflage  through  the  lungs.  As  the 
blood  proceeds  in  its  mazy  route  through  the  different  parts 
of  the  arterial  fyftem,  it  is  gradually  robbed  of  its  concommi- 
tant  oxygene  or  bafe  of  vital  air,  by  the  myfterious  aflion  of 
the  animal  fyltem.  The  confequence  of  this  fpoliation  i», 
that  the  florid  arterial,  affumes  a  much  darker  colour,  and  fuf- 
fers  finally  a  complete  tranfmutation  into  venous  blood.  In 
this  latter  ftate  the  putrefactive  proccfs  is  lefs  apt  to  com- 
mence, becaufe  the  blood  contains  lefs  oxygene  in  a  ftate  of 
intimate  mixture,  or  perhaps  I  might  with  more  propriety 
fay,  in  a  ftate  of  combination.  For  in  proportion  as  the  bafe 
of  vital  air  is  more  intimately  blended  with,  and  therefore 
more  nearly  approximated  to,  the  conftituent  parts  of  the 
blood,  the  more  powerfully  can  it  co-operate  with  other  aux- 
iliary agents,  in  inducing  thefe  parts  to  affume  that  intcftine 
motion,  which  conftitutes  the  putrefactive  procefs.  Although 
our  learned  author  is  decidedly  of  opinion,  that  putrefaction 
commences  more  readily,  if  vital  air  be  excluded  altogether 

from 


32  OF  THE  BILE. 

§  375- 
The  fubfhnce  of  the  liver  is  of  a  nature,  fid 
generis,   and  may  be  readily  diftinguifhed,  at  firft 

from  the  putrefying  fubftances,  yet  it  is  now  well  known, 
that  the  very  reverfe  of  this  is  true.  Exclude  vital  air  from 
a  body,  in  the  compofition  of  which  none  of  this  energetic 
fluid  exifts,  and  you  thereby  embalm  that  body  in  a  degree 
equal,  if  not  fuperior  to  the  embalmment  of  the  unperifhable 
mummies  of  the  Eaft. 

No  body,  whatever,  is  capable  of  taking  on  the  putrefac- 
tive procefs,  that  does  not  contain  in  its  compofition  more 
or  lefs  of  thofe  fimple  fubftances  that  belong  to  the  clafs  of 
inflammables.  Reafoning  therefore  a  priori,  or  climbing  the 
arduous  fteeps  of  fcience  by  the  more  laborious  fteps  of  expe- 
riment and  obfervation,  we  are  warranted  in  either  cafe  to 
conclude,  that  putrefaction  confifts,  in  a  very  considerable 
degree,  in  the  intimate  combination  of  the  bafe  of  vital  air  to 
certain  fubftances  of  an  inflammable  nature.  Both  the  pri- 
mary elements  of  which  putrcfiablc  bodies  are  compofed,  and 
alfo  the  refuhs  of  actual  putrefaction,  co-operate  in  the  efta- 
blifliment  of  the  fame  conclufion. 

It  is  certainly  a  truth,  that  vital  air  is  as  eflential  to  the 
putrefactive  procefs  as  it  is  to  the  fupport  of  combuftion,  or 
the  continuance  of  animal  life. 

Upon  the  whole,  we  may  without  the  fmalleft  hefitation 
conclude,  that  the  former  opinions  of  phyfiologiits  refpecting 
the  fuppofed  putrefcent  difpofition  of  the  hepatic  blood,  are 
wholly  infupportable  by  argument  or  fact,  being  indeed  di- 
rectly oppofed  to  the  literal  refult  of  pofitive  experiment; 
2  and 


OF  THE  BILE.  33 

light,  from  that  of  all  the  other  vifcera  of  the 
body  :  it  confiits  of  .1  parenchyma  of  a  well  known 
colour  and  very  tender  texture  :  this  parenchyma 
is  abundantly  fupplied  with  nerves,  with  lympha- 
tic vefTels  (very  vifible  on  both  furfaces),  with  bi- 
liferous  dufh,  and  finally  with  blood-veffels,  from 
whence  thefe  duels  originate :  with  refpecl  to 
thefe  blood-veffels,  fome  of  which  are  remarkably 
large,  we  will  immediately  (late  a  few  obfervations 
on  each  of  their  feveral  orders. 

§  376- 

The  firft  vefTel  which  here  prefents  itfelf  for 
our  confideration  is,  the  vena  port  arum  ^  which 
diners  very  widely  from  every  other  portion  of 
the  venous  fyflem,  not  only  in  its  fingular  appear- 
ance, but  alfo  in  the  peculiarity  of  its  courfe  and 
diflribution,  of  which  a  few  words  were  fpoken 
on  a  former  occafion  (§  87).  This  large  vefTel 
is  formed  by  the  conflux  of  by  far  the  greater 
number  of  the  venous  branches  that  originate  and 
run  from  the  vifcera,  £  mated  in  the  lower  part  of 
the  abdomen,  and  is  invented  and  ftrengthened  by 

and  therefore,  that  the  pious  eulogia  fo  profufely  beflowed 
on  the  powers  of  the  animal  economy,  in  being  able  to  form 
an  antifeptic  out  of  a  highly  putrefcent  fluid,  appear  to  be  as 
rifionary  and  hypothetical,  as  nature's  final  intention  in  the 
preparation  orthis  fluid  was  thought  to  be  beneficent,  and  hzt, 
procefs  itfelf  beautiful,  and  interefting. 

vol.  11.  G  a  ecl- 


3*  OF  THE  BILE. 

a  cellular  covering,  commonly  known  by  the  name 
of  capfula  GUJfunil.  No  fooncr  does  this  trunk 
make  its  entrance  into  the  liver,  than  it  is  divided 
into  feveral  branches,  which  as  they  run  in  vari- 
ous directions  through  its  fubftance,  fuffer  flill  far- 
ther divifions,  till  they  are  finally  encreafed  to  a 
countlefs  number  of  the  molt  fubtle  ramifications, 
which  pervade,  with  the  utmofl  minutenefs,  every 
portion  of  this  vifcus.  This  whole  fyllem  of  the 
vena  portarum  was  formerly  compared,  by  Galen, 
to  a  tree,  the  roots  of  which  are  difperfed  through- 
out the  whole  cavity  of  the  abdomen,  while  its 
branches  are  encloied  in  the  more  contracted  vo- 
lume of  the  liver. 

§  377- 

Another  blooJ-vefTel  of  a  different  kind,  with 
which  the  liver  is  furnillied,  is  the  artcria  hepatica. 
This  veiTel  originates  from  the  caeliac  artery,  and 
although  far  inferior  to  the  vena  portarum,  both 
in  its  capacity  and  in  the  number  of  its  branches, 
is,  notwithstanding,  divided  into  ramifications  of 
aftonifiimg  fubtility,  and  is  alfo  diftributed  with  a 
great  deal  of  minutenefs  throughout  every  part  of 
the  liver. 

s  37»- 

The  extreme  terminations  of  both  the  forego- 
ing kinds  of  vcllels,  end  in  genuine  veins,  which 

gradually 


OF  THE  BILE,  3; 

gradually  uniting,  form  by  their  general  conflux, 
certain  large  venous  trunks,  that  lofe  themfelves 
finally  in  the  inferior  vena  cava. 

§  379- 
Thofe  extreme  terminations,  by  which   thefe 

fmall  branches  of  the  vena  portarum  and  arteria 
hepatica  become  radicles  to  the  vena  cava,  form 
a  very  fubtle  vafcular  texture,  exhibiting  a  fingu- 
lar  and  ftriking  appearance,  as  if  the  veifels  were 
convoluted,  or  wound  up  into  globes  of  incon- 
ceivable minutenefs.  Thefe  globular  bodies  im- 
pofed  fo  effectually  on  Malpighi,  as  to  induce  that 
illuftrioas  phyfiologift  to  confider  them  as  glandu- 
lar, hexagonal,  and  hollow  kernels,  deitined  to 
conflitute  the  immediate  chambers  of  fecretion. 

§  38o. 
From  thofe  fame  globular  convolutions  of  blood- 
veffels  arife,  laitiy,  the  port  blliarii.  Thefe  are 
very  tender  ducts,  which  convey  the  galliih  liquid 
from  the  blood,  and  completely  eliminate  the  fame 
from  the  fyftem  of  the  liver,  through  the  duclus 
hepaticus  communis,  a  canal  which  they  form  by 
their  general  conflux. 

§   38l« 

It    is    common    for   phyfiologiits    to    enquire, 

from  what  kind  of  blood  the  bile  is  immediately 

G  2  fecrcted  ; 


id  OF  THE  BILE. 

i'ccrctcd  ;  whether  from  arterial,  or  from  that  con- 
tained in  the  vena  poriarum  ? 

Although  the  former  of  thefe  opinions  appears, 
on  the  firfb  view  of  the  fubjelt,  to  be  rendered 
mod  probable  from  the  analogy  of  other  fecre- 
tions,  which  are  evidently  the  refult  of  arterial 
aftion,  yet  from  a  more  accurate  invefligation  of 
the  matter  we  will  readily  be  convinced,  that  by  far 
the  greater  part,  if  not  indeed  the  whole,  of  the  bi- 
liary fecretion,  is  derived  from  the  vena  portarum  : 
the  blood  of  this  vefTel  being  lurid,  and  highly  im- 
pregnated with  phlogidon,  correfponds  precifely 
with  the  nature  of  the  bile  ;  but  how  extremely 
difFerent,  on  the  o:her  hand,  are  the  habit  and 
conftitution  of  the  florid  and  fiery  arterial  blood, 
which  the  cseliac  artery  tranfmits  from  the  aorta 
immediately  to  the  liver  ! 

"With  refpecl:  to  arguments  drawn  from  analogy 
we  may  obferve,  that  as  the  vena  portarum  is  fub- 
jctfted  to  an  arterial  diflribution,  fo  it  may,  in  like 
manner,  poffefs  the  power  of  performing  an  arte- 
rial fun&ion  :  this  fame  opinion,  for  which  we  con- 
tend, appears  alfo  to  derive  additional  fupport 
from  the  analogy  which  exifts  between  the  liver 
and  the  lungs  :  to  perform  the  leading  function  of 
thefe  laft  mentioned  vifcera,  is  dcubtlefs  the  imme- 
diate defoliation  of  the  large  pulmonary  arteries  j 

whereas, 


OF  THE  BILE.  3? 

whereas,  on  the  other  hand,  the  bronchial  artery- 
is  only  fubfervient  to  the  nourifhment  of  the  parts, 
on  which  it  is  diftributed  : — the  difcharge  of  an 
office,  fimilar  to  this  latter,  is  alfo,  if  we  be  net 
greatly  deceived,  the  more  immediate  deflinaiiou 
of  the  arteria  hepatlca.  Notwithflanding  what 
we  have  here  advanced,  we.  are  (till  ready  to  ac- 
knowledge, that  the  hepatic  artery  may  poffibly 
contribute  fome  what  towards  the  fecretion  of  bile  ; 
but,  that  its  influence,  in  this  refpecT:,  is  indeed 
very  inconfiderable,  and  not  yet  fufficiently  afcer- 
tained  and  demonftrated,  are  pofitions-to  which 
we  fubferibe  with  the  utmeff.  confidence. 

382. 

The  biliary  hepatic  liquor,  when  once  fecreted, 
flows  in  a  gentle  but  uninterrupted  ftreamlet 
through  the  hepatic  duel ;  and,  when  the  intejli- 
num  duodenum  is  empty,  glides  directly  onward, 
through  the  common  duel  us  cboledocus,  into  the 
cavity  of  that  vifcus  ;  but  when  the  duodenum  is 
diftended  with  chyme,  it  becomes  necefTary  for 
this  fluid  to  purfue  a  different  route,  whence  it 
regurgitates  from  the  hepatic,  and  flows  through 
the  cyjlic  duel  into  the  gall-bladder,  where  it  is 
retained  a  certain  time,  and  thence  derives  the 
name  of  cjftlc  bile. 

C3  §3** 


3«  OF  THE  BILE. 

§   S«3- 

The  gall-bladder  is  an  oblong  fack,  fomewbat 
pyriform  in  its  figure,  attached  to  the  concave  fu- 
pcrficies  of  the  liver,  and  compofed  of  three  mem- 
branes or  coats. 

Thcfe  are,  firft,  the  external,  which  does  not 
invert  the  whole  of  the  cyfl,  and  is  derived  from 
the  peritoneum. 

Secondly,  the  middle,  ufually  called  the  nervous 
coat,  which,  as  in  the  flomach,  the  inteftinal  tube 
and  the  urinary  bladder,  conflirutes  here  likewife 
the  principal  part  of  the  tone  and  firmnefs  of  the 
fac. 

And,  laflly,  the  internal,  which  bears  a  certain 
fimilirude  to  the  internal  membrane  of  the  flomach 
(§  3590  »  1'ke  tnat  n  *s  interfperfed  with  an  infi- 
nitude of  minute  blood-veffels,  and  like  that  it  is 
alfo  marked  by  rugas  or  wrinkles,  which  form, 
here  and  there,  fine  net-like  checkerings,  that  ex- 
hibit the  appearance  of  the  mod  exojuifitely  ele- 
gant lattice-work. 

§  384- 

The  neck  of  the  gall-bladder  is  conical,  and 
forms,  by  its  termination,  the  cjjiic  duel,  which 

purfues 


OF  THE  BILE.  i9 

purines  not  a  direct,  but  fomewhat  circuitous  or 
terpentine  route,  and  is  furnifhed  with  a  few  mi- 
nute valves  of  alunated  or  falciform  figure. 

§  385- 

The  gall-bladder  retains  the  bile,  when  once 
received,  til!  that  liquor  either  flows  out  fpontane- 
ouflyj  in  confequtnee  of  being  favoured  by  a  re- 
cline.i  and  fomewhat  fupirie  pofition  of  the  body, 
or  till  it  is  emulged  from  the  cyfl  by  the  prefllire 
of  the  neighbouring  inteftines,  namely,  the  jeju- 
num and  ileum,  or  by  the  occafional  pa  flag  e  of 
hardened  fecces  through  the  tranfverfe  colon. 

Different  ftimuli  acting  on  the  duodenum  have 
alfo  the  effect  of  folieiting  a  more  copious  effuflfn 
of  bile  into  the  cavity  of  that  intefline. 

The  remarkable  contractility  of  the  gall-blad- 
der, evidenced  and  fatisfactorily  eftablifhed  by  live 
diflecTions  and  certain  pathological  phenomena, 
(although  this  fac  be  indeed  completely  deftitute 
of  all  genuine  irratibUity \) ',  (§  o°7-)->  w'^  appear 
to  contribute,  not  a  little,  to  the  excretion  of  the 
bile ;  efpecially  when  wc  confider  the  ftimulant 
impreflion  which  this  fluid,  after  retention  in  the 
cyfl,  rnufl  make  on  its  furrounding  parietes  or 
walls. 

Q  4.  $  3S6. 


4*  OF  THE  BILE. 

§   386. 

For  although  the  cyjlic  exhibits,  in  its  general 
properties,  the  mcfl  finking  fimilitude  to  the  he- 
■patl:  bile  (§  382.),  it  is  notwithstanding  concen- 
trated, as  it  were,  by  reft  and  ftagnation,  and 
thence  rendered  more  tenacious  and  bitter  :  this 
effect  appears  to  be  owing,  in  a  particular  man- 
ner, to  the  lymphatic  veifcls  of  the  cyft,  which 
flowly  abforb  the  aqueous  parts  of  the  bile,  while 
thus  enclofed  and  retained  in  a  quiefcent  (late. 

§  387- 

We  proceed  now  to  the  confideration  of  the 
bile  itfelf.  This  is  an  animal  fluid  of  the  higheft 
dignity  and  importance  in  the  living  fyftem  :  its  na- 
ture and  ufes  have,  for  twenty  pears  pad,  laid  a 
foundation  for  more  literary  controverfies  among 
phyfiologifts,  than  have  exifted  refpecling  any 
other  fluid  that  belongs  to  the  body  of  man. 

What  we  fhall  advance  on  this  fubjeft  will  re- 
late immediately  to  the  cyftic  bile,  as  this  is  to  be 
efteemed  the  more  perfeel  of  the  two,  and  is  there- 
fore in  a  ftate  more  favourable  for  fuccefsful  in- 
vefligation. 

§  38s. 

Bile,  taken  from  the  recent  corpfe  of  an  adult 
fubjedfc,  who  had  not  previoufly  laboured  under 

any 


OF  TH£  BILE.  41 

any  difeafe,  is  a  liquor  fomewhat  vifcid,  of  a  faint 
green  colour,  inclining  towards  a  brown,  inodo- 
rous, and,  if  compared  with  the  gall  of  brutes,  of 
a  llightly  bitterilh  tafte. 

§  389- 

Although  the  condiment  parts  of  this  fluid  nei- 
ther feparate  from  each  other  fpontaneoufly,  nor 
yet  by  fo  fimple  a  mode  of  treatment  as  is  fufficient 
to  produce  that  effect  on  the  parts  that  compofe 
the  blood,  they  may,  notwithstanding,  be  fabje<ft- 
cd,  without  much  difficulty,  to  fuch  an  examina- 
tion as  will  make  it  appear,  that  they  doubtlefs 
pofTefs  and  exhibit  a  certain  analogy  to  the  ele- 
mentary parts  of  the  blood,  though  this  analogy 
fliould  not  be  purfued  to  too  great  an  extent. 

The  bile  contains,  in  the  firft  place,  an  aqueous 
menflruum,  which  has  been  denominated  by  fome 
late  phyfiologiils,  its  falroary  part  :  this  may  be 
aptly  enough  compared  to  the  aqueous  portion, 
and  refembles  alio,  though  not  in  every  particu- 
lar, the  ferum  of  the  blood. 

From  the  bile  we  can  alfo  feparate  and  procure 
a  fmall  portion  of  a  white  and  grumous  fubftance, 
which  may  be  faid  to  pofTefs  a  certain,  though  re- 
mote  refemblance   to   the    plaflic  lyrftph  of  the 

blood. 

Finally, 


42  OF  THE  BILE. 

Finally,  the  mod  flriking  and  important  princi- 
ple which  the  bile  contains  is  the  nutter  of  phlo- 
glfton^  derived  in  large  quantities  from  the  blood 
of  the  vena  portarum,  which  is  highly  impreg- 
nated with  this  fubtle  element. 

§  39°- 
This  active  inflammable  part  evidently  manifefts 
its  exiftence  in  dried  bile,  but  more  efpecially  in 
gall  ftones,  by  burfting  immediately  inco  flame, 
when  placed  in  contact  with  a  burning  fubicance. 
To  the  action  and  influence  of  this  principle  inuflj 
we  attribute  thofe  ftriking  and  lingular  qualities, 
formerly  enumerated,  fuch  as  colour,  taife,  &c. 
which  ferve  to  diilinguilh  the  bile  from  the  other 
inquiline  humours  belonging  to  the  fyftem  ;  and 
from  the  fame  fource  muff  we  a'.fo  derive  the  other 
remarkable  properties  of  this  fluid,  which  fliall  be 
mentioned  hereafter. 

1,39V 

The  bile  is  not  of  fuch  a  nature  as  to  polTefs, 
like  foap,  an  equal  affinity  to  oil  and  water,  and 
thus  ferve  to  mix  and  intimately  combine  thefe 
two  elements  together.  The  contrary  opinion 
(which  was  crroneoufly  entertained  on  this  fubjecl 
by  Boerhaave,  and  afterwards  by  Schroder)  was 
formerly  invalidated  and  refuted  by  certain  re- 
markable experiments  of  my  own  (fmce  confirmed 

and 


OF  THE  BILE.  43 

and  further  increafed  by  other  writers),  and  is 
now  entirely  repudiated  by  the  greater  number  of 
phyfiologifts.  On  the  other  hand,  if  bile  be  ap- 
plied to  the  two  foregoing  elements,  i.  e.  oil  and 
water,  when  in  a  {late  of  intimate  mixture  and 
combination,  it  produces  an  evident  difunion  and 
feparation  of  them  from  each  other.  This  fluid 
pofTefTcs  indeed  no  alkaline  properties,  but  is,  not- 
withstanding, equally  unfriendly  to  the  exigence 
of  acid  acrimony,  to  fermentation,  and  to  putre* 
faction, 

§  392- 

By  confidcring  with  due  attention  the  foregoing 
obfervations,  we  may  eafily  afcertain  the  true,  the 
important,  and  the  diversified  ufes  of  the  bile,  in 
the  procefs  of  chylification. 

For  in  the  firil  place,  from  that  equable  and 
uniform  chymous  pulp  which  the  {lomach  has  dis- 
charged into  the  duodenum,  which  the  pancreas 
has  diluted  by  an  eflufion  of  its  own  juice,  and 
which  moves  fpontancouily  onward  to  the  cavity 
of  the  fmall  inteftincs,  it  gradually  precipitates  the 
faeces,  and  thus  feparatcs  from  them  that  crearn- 
jike  fluid  denominated  cbvle. 

The 


44  OF  THE  BILE. 

The  bile  itfclf  differs,  at  the  fame  time,  a  divi- 
sion into  two  parts,  the  one  aqueous,  the  other 
phlogiftic.  The  latter  part  adheres  to  the  faeces, 
tinges  them,  and  is  afterwards  difcharged,  along 
with  them,  out  of  the  body  ;  whereas  the  former 
appears  to  be  mixed  with  the  chyle,  and  re-con- 
dufted  back  to  the  mafs  of  blood. 

Thus  the  abundant  phlogift.cn,  now  become 
troublefome  and  noxious  to  the  blood,  is  firft  di- 
rected to  the  liver,  where  it  is  rendered  fubfcrvient 
to  the  formation  of  a  fragular  and  very  important 
humour :  After  this  humour  has  fully  anfwered 
the  end  of  its  deftination,  its  fuperfluous,  or  rather 
noxious  part  is  included  among  the  excrements, 
and  finally  eliminated' from  the  fyftem. 

A  further  ufe  of  the  bile  is,  to  evolve  and  ex- 
terminate from  the  alimentary  canal,  the  fixed  air, 
which  had  been  hitherto  confined  among  the  chy- 
mous  mafs  :  it  appears  alfo  to  act  on,  and  aid,  the 
inteflinal  tube,  by  means  of  its  (limulus,  thus  ex- 
citing it  to  perform  its  periftaltic  motion  with 
greater  vigour  and  energy. 

I  filently  pretermit  a  variety  of  other  ufes,  com- 
monly attributed  to  the  bile,  which  appear  to  me 
to  reft:  on  more  doubtful  3nd  equivocal  evidence, 

fuel), 


OF  THE  SPLEEN.  45 

fuch,  for  inftance,  as  its  power  of  regurgitating 
into  the  ftomach  when  empty,  and  thus  exciting 
appetite,  a  phenomenon  that,  in  my  opinion,  can 
very  fddom  occur  in  a  well  formed  and  healthy 
human  fubject. 


SECT.    xxxr. 

OF  THE  FUNCTION  OF  THE  SPLEEN. 
§    393' 

1  HE  fpleen  is  very  intimately  connect- 
ed with  the  liver,  not  only  by  an  intercourfe  of 
veffels,  but  alfo  by  the  affinity  and  fubferviency  of 
its  function :  it  is  iituated  in  the  left  hypochon- 
driac region,  oppofite  to  the  liver ;  its  figure  is 
oblong,  generally,  indeed,  accommodated  to  the 
fituation  of  the  neighbouring  vifcera  with  which  it 
lies  in  contact :  it  is  fubjedl  however,  to  multiplex 
varieties  with  regard  to  form,  number,  and  other 
fpecies  of  lufi  nature,  or  preternatural  pheno- 
mena. 

§  394- 
Its  colour  is  livid,  its  texture  altogether  lingu- 
lar, being  foft,  friable,  eafily  lacerated,  and  there- 
fore 


43  OF  THE  SPLEEN. 

fore  fecurely  protected  by  two  membranous  cover-* 
ings,  the  internal  of  which  belongs  properly  to 
the  fpleen  itfelf,  while  the  external  appears  to  be 
derived  from  the  omentum. 

§  395- 
The  fituation  and  fize  of  the  fpleen  are  now  and 

then,   no  lefs  than  its  figure,  fubject  to  finking 

and  lingular  variations,  arifing  in  a  great  meafure 

from  the  different  {fates  of  the  ftomach,  with  re- 

fpect  to  fulnefs  and  depletion  :   thus,  for  example, 

when  the  ftomach  is  empty,  and  hangs  in  a  loofe 

and  depending  pofition,    the  fpleen  is  diflended 

with  blood  ;  but  when  the  former  vifcus  becomes 

turgid  again,   the   latter  is  emulged,  and  confe- 

quently  diminifhed   in   bulk  by  the  preffure  to 

which  it  is  fubjected. 

The  fpleen  is  alfo  agitated  by  another  perpetual, 
though  gentle  and  uniform  motion,  in  confequence 
of  refpiration,  being  fubjectcd  to  the  immediate 
action  of  a  primary  inflrument  of  that  function, 
namely,  the  diaphragm. 

§    396. 
The  texture  of  the  fpleen,  phyfiologtfls  former- 
ly fuppofed  to  be  cellular,  and  uniformly  compared 
it  to  the  corpora  cavernofa  of  the  penis :  this  opi- 
nion, however,  is  evidently  founded  in  error,  and 

haa 


OF  THE  SPLEEN. 


41 


has  been  very  fatisfaclorily  refuted  by  a  more  ac- 
curate examination  of  the  human  fpleen.  For, 
from  fuch  examination  we  learn,  that  almoft  the 
whole  volume  of  this  vifcus  is  compofed  of  blood 
veil  els,  extremely  large  in  proportion  to  its  fize  ; 
fo  that  it  is  fupplied  with  a  greater  profufion  ol 
blood,  than  any  other  part  belonging  to  the  body 
of  man. 

§  397- 
The  fplenic  artery,  confpicuous  (agreeably  to 
the  experiments  of  Wintringham)  on  account  of 
the  aftonifhing  finenefs  and  drength  of  its  coats, 
is  divided  into  an  infinitude  of  minute  ramifica- 
tions, which  conftitute  finally,  by  their  evanefcent 
extremities,  very  fmall  pulpy  pencils :  thefe  pencils 
afford  origin,  again,  to  fine  filiform  veins,  that 
conftitute  by  their  gradual  confluence,  large  and 
lax  trunks  highly  capable  of  dilatation. 

<  §  398- 

This  vaft  congeries  of  blood  veffels,  is,  how- 
ever, knit  together  and  fupported  by  a  fmall  quan- 
tity of  cellular  parenchyma,  from  whence  the  ab- 
forbent  vtffels  arife,  the  trunks  of  which  run  on 
the  plain  or  flat  fide  of  the  fpleen,  between  the 
two  membranous  coverings,  of  which  we  have  al- 
ready fpoken. 

§  399- 


4$  OF  THE  SPLEEN. 

§  399- 
This  texture  of  the  fpleen,  fo  very  lax  and  high- 
ly capable  of  admitting  blood,  correfponds  admi- 
rably with  what  we  formerly  faid  refpecting  the 
fanguineons  difteniion  of  this  vifcus  (§  395)  :  and 
we  may  further  obferve,  that  the  phenomena  of 
the  congeftion,  and  tardy  progrtffive  motion  of  this 
crimfon  fluid  in  the  fpleen,  confidered  in  conjunc- 
tion with  the  nature  of  the  furrounding  and  conti- 
guous vifcera,  tend  not  a  little  to  illuftrate  the  pe- 
culiar flate  and  condition  of  the  fplenic  blood, 
which  of  themfelves  appear  to  ftied  confiderable 
light  on  the  function  of  this  myfterious  vifcus,  a 
fubject  of  fuch  repeated  controverfies  among  phy- 
lioiogifte. 

§  4°°- 
The  blood  contained  in  the  veins  of  the  fpleen 
is  very  fluid,  diflblved,  coagulated  with  the  utmofl: 
difficulty,  and  admits  of  but  a  flight  and  partial 
reparation  of  the  ferum  from  the  crafiamentum  ; 
its  colour  is  alfo  livid  and  obfcure,  as  in  the  foe- 
tus ;  all  which  phenomena  appear  evidently  to 
combine  in  ascertaining  and  even  demonftrating 
the  prefence  of  an  abundant  quantity  of  the  phlo- 
giflic  element.  That  this  element  is,  however, 
unequivocally  prefent  in  large  quantities,  I  further 
afcertained  to  my  entire  fatisf action,  by  the  follow- 
ing fi;np!e  and  conclufive  experiment :   to  the  ac- 

1  tion 


OF  THE  SPLEEN.  4y 

tion  of  pure  dephlogifticated  air,  I  expofed  recent 
fections  and  ilices  of  the  fpleen  of  a  human  fubject; 
no  fooner  were  thefe  pieces  brought  in  contact 
with  this  vital  fluid,  than  they  were  overfpread 
with  a  very  florid  and  beautiful  crinifon  blufh, 
while  the  air  itfelf,  thus  dcipoi'ed  of  its  native 
fire,  was  on  the  other  hand,  contaminated  by  the 
fplenic  phlogifton. 

§  4-OI- 
When  we  contemplate  the  foregoing  circum- 
ftances  collectively,  and  conllder  in  the  laft  place, 
that  the  fpleen  is  the  only  vifeus  of  a  fimilar  nature 
wholly  unfurnimed  with  any  veflige  of  an  excre- 
tory duct,  fave  thofe  vtffels  which  we  have  alrea- 
dy laid  run  to  the  liver,  we  are  obliged  from  the 
force  of  concurring  telUmony  to  conclude,  that 
the  fole  office  of  the  organ  now  under  confidera- 
tion,  is  to  act  in  fubferviency  to  the  function  of  the 
liver,  and  contribute  towards  the  formation  of 
bile  by  the  co-operation  of  its  phlogiftic  parts. 

§  402- 
This  opinion  is  flill  farther  fubitantiated  by  a 
Very  curious  and  ufefui  oMervation,  made  on  fuch 
individuals  of  the  animal  kingdom,  as  have  been 
deprived  of  the  fpleen  by  excifion.  It  appears 
that  in  animals  fubjected  to  this  operation  (v/hich, 
however  Angular  and  feemingly  barbarous,  has 
vol,  ii,  D  been, 


$o  OF  THE  OMENTUM. 

been,  notwithstanding,  very  frequently  performed 
from  remote  periods  of  time)  the  cyftic  biie  has 
been  uniformly  afterwards  found  to  be  pale,  weak- 
ly impregnated  with  phlogifton,  and  difpofed  to  a 
grume-like  coagulation  of  its  lymphatic  portion. 


SECT.     XXXII. 
OF  THE  FUNCTION  OF  THE  OMENTUM. 

§  4°3- 

JL  H  E  omentum  gafkrocolium,  or  omentum 
magnum,  (fo  called  to  diftinguiih  it  from  the  par- 
*uum  or  hepaticogaftricwii),  is  indeed  a  very  lingu- 
lar produ&ion  of  the  peritoneum,  originating  im- 
mediately from  the  external  coat  of  the  llomach. 

§  4G4- 
For  notwithftanding  the  continuations  of  the 
peritoneum,  in  the  abdominal  cavity,  be  almofl  innu- 
merable, and  although  all  the  parts  contained  in 
this  cavity,  whether  viewed  collectively  or  indivi- 
dually, be  fo  uniformly  invefteg  by  it,  that,  on 
opening  the  abdomen,  it  is  impbfTible  to  difcovcr 
a  lingle  vifcus  which  this  membrane  does  not  em- 
brace, yet  the  modes  in  which  it  furnimes  this 

covering 


OF  THE  OMENTUM.  $f 

covering  to  the  feveral  vifcera,  are  fo  diverfnied, 
as  to  merit  a  divilion  into  different  claffes. 


Thus,  for  example,  the  abdominal  cavity  con- 
tains certain  parts,  over  which  the  peritoneum  is 
only  fpread  in  fuch  a  partial  and  Ample  manner, 
as  to  invell  but  one  of  their  furfaces ;  this  obfer- 
vation  may  be  applied  particularly  to  the  kidneys, 
the  inteflinum  rcclum,  the  veftca  urinaria,  and  in 
fome  meafure  alfo,  to  the  pancreas  and  gall- 
bladder. 

There  are  alfo  other  vifcera,  which,  notwith- 
{landing  their  attachment  and  adhefion  to  the  fur- 
rounding  parietes  of  the  abdomen,  yet  projeft  alfo 
to  a  conliderable  diftance  into  the  abdominal  ca- 
vity itfelf,  and  derive  from  the  peritoneum  a  co- 
vering, which  inverts,  by  far,  the  greater  part  of 
their  external  furfaces  :  of  this  defcription  are  the 
liver,  the  fpleen,  and  even  the  fromach  and  female 
uterus,  to  which  we  may  add,  finally,  the  teftes 
of  a  male  foetus,  previoufly  to  their  defcent  into 
the  ferotum. 

Confiderably  different  again,  (in  point  of  peri- 
toneal covering),  from  both  the  foregoing  claffes 
of  vifcera,  is  the  whole  of  the  inteftinal  tube,  ex- 
cept that  portion  which  is  denominated  intejiinum 
rectum.  This  tube  paffes  through  the  adommal 
D  z  cavity 


§i  O'F  THE  OMENTUM. 

cavity  in  fuch  a  manner,  as  to  carry  along  with  it, 
two  remarkably  broad  proceffes  of  the  peritoneum, 
namely  the  mefentery  and  mefocolon,  to  which  it 
adheres  in  a  ftate  of  fufpenfion :  under  the  fame 
clafs  with  the  two  preceding  proceffes,  may  we 
alfo  arrange  thofe  fmgular  peritoneal  productions, 
denominated  the  broad  ligaments  of  the  uterus. 

But  fmally,  the  moft  extenfive  of  all  is  that  pe- 
culiar continuation  of  the  peritoneum  called  the 
omentum.  This  production  is  a  large  empty  fac 
of  a  very  delicate  texture,  that  hangs  in  a  depend- 
ing pofition  from  the  great  curvature  of  the  flo- 
mach  ;  it  is  fpread  over  the  region  of  the  fmall  in^ 
tejiines  in  particular,  nicely  adapts  itfelf  to  their 
irregular  convexities,  and  dips  down,  in  fome 
meafure,  into  their  numerous  interfaces. 

§  4°6- 
Befides  the  blood  veffels  by  which  the  omen- 
tum is  painted,  it  is  alfo  marked  by  numerous 
,fir'uz  or  broad  lines  of  adipofe  fubflance,  which 
meet,  interfecl:,  and  thus  form  a  variety  of  reticu- 
lar intertextures,  from  whence  the  membrane  has 
received  the  name  vernaculwn.  In  perfons  dif- 
pofed  to  obefity  this  adipofe  fubflance  encreafes 
now  and  then  to  fuch  a  fize,  as  to  become  not  only 
troublefome  but  even  dangerous :  it  is  alfo  this 

adipofe 


OF  THE  OMENTUM. 


53 


adipofe  portion  that  affords  origin  to  that  oily 
haliius  by  which  the  omentum  is  conftanrfy  fur- 
rounded  and  moiftened. 

§  4°7- 
It  has  been  the  opinion  of  certain  celebrated 

characters,  and  a  further  attempt  was  made  by 
the  illuftrious  Haller  to  prove,  that  the  fat  con- 
tained in  the  omentum  is  deftined  to  be  taken  up 
by  abforption  and  conveyed  to  the  liver,  for  the 
purpcfe  of  fupplying  the  bile  with  its  oily  portion, 
8zc.  With  refpefi  to  the  truth  of  this  opinion, 
however,  I  mud  fti'l  be  permitted  to  entertain  and 
exprefs  a  ferious  doubt,  having  never  yet  been 
convinced  that  found,  uncontaminated,  bile  con- 
tains any  oil ;  nor  have  I  ever  been  able  to  difco- 
ver  any  orifices  fubfervient  to  fuch  an  abforption, 
not  even  in  frogs  themfelves,  where  Malpighi  al- 
leged, and  even  attempted  to  prove,  their  exif- 
tence  ;  much  lefs  in  that  part  which  is  the  fubject 
of  our  prefect  confideration,  namely,  the  omentum 
of  man. 

§  408. 
What  appear?,  from  the  nature  and  fituation  of 
the  part,  as  well  as  from  the  concurring  belief  of 
all  phyfiologifts  of  the  prefent  day,  to  be  a  much 
more  unequivocal  ufc  of  the  omentum,  is,  to  lu- 
bricate the  inteflines,  and  by  that  means  aid  and 
D  3  facili- 


54  OF  THE  OMENTUM. 

facilitate  their  perpetual  motion.  The  fame  ap- 
pear alfo  to  be  the  ufe  and  deftjnaticn  of  certain 
fimilar,  but  fmall,  adipofe  bur/a,  by  which  tne 
colon  and  reclwn  are  inverted. 

The  omentum  alfo  further  ferves  to  prevent  the 
occurrence  of  an  adhefion  between  the  inteftines 
and  peritoneum,  by  which  the  whole  oitice  of  the 
primse  viae  would  be  fubverted. 

§  4°9- 
That  this  adipofe  curiam  is  dfftined  to  fcrve  as 
a  defence  againft  cold,  (though  an  opinion  very 
generally  received),  appears,  notwithstanding,  to 
reft  on  evidence  of  a  more  qqeftionable  nature : 
the  omentum  of  a  man  in  perfect  health,  which 
ought  by  no  means  to  be  burrhened  with  an  accu- 
mulation of  fat,  is  indeed,  but  very  illy  calculated 
to  anfwer  fuch  an  intention. 

When  we  confider,  in  the  mean  time,  the  An- 
gular ft rucTure  of  the  two  omenta,  more  efpecially 
of  that  denominated  omentum  parvum  or  gaftrohc- 
paticum,  it  appears  fufEciently  probable,  that  be- 
fides  the  ufes  already  enumerated,  the  latter  is  ftill 
deftined  for  another,  of,  perhaps,  even  fupremc 
importance,  which  is  as  yet  unknown  to  us,  and 
which  future  refearches  in  comparative  anatomy 
•■•■  ;:1  be  alone  able  to  develope. 

SECT, 


OF  THE  INTESTINES.  55 

SECT.     XXXIII. 
OF  THE  FUNCTIONS  OF  THE  INTESTINES. 

§  410- 

JL  HE  inteftinal  tube  itfelf  (before  which 
the  omentum  is  fpread,  and  into  which  we  have 
already  feen  the  chyme  conveyed,  in  order  to  be 
further  elaborated  and  fufficiently  fitted  for  the 
feparation  of  chyle),  is  divided  into  two  leading 
portions,  namely,  the  fmall  and  great ;  of  the 
functions  of  which  we  will  now  treat  feparately 
and  in  order. 

§   411- 
The  fmall  portion  of  inteftines  is  again  fubdi- 
vided  into  three  parts,  namely,  the  duodenum,  je- 
junum, and  ileum. 

The  duodenum  derives  its  name  from  the  cir- 
cumilance  of  its  lencrth. 

O 

The  jejunum  from  that  of  its  general  habit,  be- 
caufe,  in  a  recent  cprpfe,  it  appears  collapfed  and 
empty  as  it  were,  even  although  it  contain  at  the 
fame  time  a  quantity  of  pulpy  chyme.  In  the 
third  divifion,  called  ileum,  the  chyme  depofits  its 
faeces,  and  fuffers  an  evolution  of  its  air,  which 
D  4  had 


56  OF  THE  INTESTINES. 

had  been  hitherto  fixed,  fo  that  this  laft  of  the 
fmall  inteflines,  being  at  the  fame  time  the  longeft, 
and  deriving  its  name  from  its  circumvolutions, 
appears  more  turgid,  fomewhat  inflated,  and  mark- 
ed here  and  there  with  fmall  bubble-like  emi- 
nences, af:er  the  manner  of  the  large  portion  of 
tms  tube. 

§   412. 

The  coats  of  the  fmall  inteflines  are  perfectly 
fimilar  to  thofe  compofing  the  flcmach,  of  which 
we  have  already  fpoken  (§  359.) 

The  external  is  a  production  of  the  mefentcry. 

The  mufcular  coat  confifts  of  two  orders  of 
■fibres,  to  wit,  longitudinal,  which  are  interrupted 
in  their  courfe,  and  run  rather  externally,  efpeci* 
ally  on  that  fide  of  the  intefline  that  looks  in  a 
contrary  direction  from  the  mefemery  ;  and  more 
internal,  annular,  or  falciform  fibres,  which  are 
calculated  to  contra&  or  narrow  the  diameter  of 
the  tube  ;  whereas  the  former  are  intended  to  di- 
ininifh  its  longitudinal  extent.  On  both  the  pre- 
ceding orders  of  fibres  depends  that  exquifitely 
energetic  and  pertinacious  irritability  of  the  intes- 
tines, of  which  we  have  fpoken  on  a  former  occa- 
sion (§  3o60 

The 


OF  THE  INTESTINES.  57 

The  nervous  coat  confifts  of  compared  cellular 
membrane ;  and  may,  by  a  very  fimple  mode  of 
treatment,  efpecially  by  blowing  into  it,  be  again 
reduced  to  a  fpongy,  foam-like  untie  :  throughout 
this  coat  a  variety  of  blood-veffels,  detached  from 
the  mefenteric,  are  diflributed  in  the  form  of  ar- 
borets  or  branching  fhrubs,  of  inimitable  elegance 
and  beauty.  As  in  the  (lomach,  fo  likewife  in  the 
interlines,  the  nervous  coat  is  the  principal  feat  of 
tenacity  and  flrength. 

Finally,  the  internal  coat  (which  merits  more 
unequivocally,  in  the  fmali  inteflines,  than  in  any 
other  part  of  the  alimentary  canal,  the  name  vil- 
lous J,  is  continued  here  and  there,  in  conjunction 
with  the  internal  furface  cf  the  preceding  mem- 
brane,  into  wave-like  productions  and  rugous 
folds,  that  in  the  inteflines,  when  inflated  and 
dried,  exhibit  a  falciform  appearance,  and  are  de- 
nominated valvules  Kerkringii. 

§  4*3- 
Of  the  villi  themfeives,  an  immenfe  number 
overfpread,  in  the  clofeft  order,  the  whole  inter- 
nal farface  of  the  fmaH  inteflines  :  their  fubtle  and 
exquifitely  elegant  vafcular  flructure,  was  firft  dif- 
covered  and  demonflrated  by  the  labours  of  the 
indefatigable  Lcibcrkuhn.  While  the  inteftines 
are  deftimte  of  chyle,  the  vilU  may  be  compared 

in 


5  8  OF  THE  INTESTINES. 

in  fome  meafure  to  fmall  purfes  hanging  in  a  loofe 
and  flaccid  pofition,  and  confifting  internally  of  a 
foft  fpongy  texture  ;  but  when  they  become  tur- 
gid, in  confequence  of  the  abforption  of  this 
milky  fluid  from  the  inteflinal  canal,  their  figure 
undergoes  fuch  a  flriking  change,  as  to  bear  no 
frnall  refemblance  to  the  phallus  efculentus  *. 

§  414- 
Thofe  villi  are  furrounded,  at  their  bafes,  by 

an  infinitude  of fmall  glandular  follicles^  which  are 
lodged  principally  in  the  nervous  coat,  and  com- 
municate by  very  minute  orifices  with  the  intefli- 
nal cavity,  into  which  they  difcharge  a  mucus  that 
ferves  to  line  and  lubricate  the  whole  internal  fur- 
face  of  that  tube. 

Thefe  minute  glands  are  commonly  fuppofed  to 
confiil  of  three  orders.  Firji,  the  Brunnerian  or 
larger  glands,  which  are  feparate  from  each  other, 
and  fituatcd  principally  on  that  part  of  the  duode- 
num, which  lies  next  to  the  pylorus. 

Secondly  the  Peyerian,  which  are  confiderably 
fmaller,  planted  in  clufters,  a>nd  lodged,  in  parti- 
cular, on  the  other  extremity  of  the  fmall  intef- 


*  A  fpecies  of 'fungus,  denominated  phallus,  from  its  ftrik- 

tines, 


ing  fimilitude  to  the  male  penis. 


OF  THE  INTESTINES.  59 

tines,  which  looks  towards,  and  is  contiguous  to, 
the  valve  of  the  colon. 

And,  Iq/l/y,  the  glands  of  Leiberkuhn,  the  mod 
minute  of  all,  of  which  about  eight  are  faid  to  be- 
long to  each  villus. 

It  ought  to  be  obferved,  however,  that  this  di- 
vifion  of  the  fources  of  mucus  appears  to  reft  on 
very  equivocal  evidence.  For  if  I  be  not  greatly 
deceived,  both  the  Brunnerian  and  Peyerian 
glands,  as  commonly  exhibited  in  plates,  are  the 
refult  of  a  vitiated  and  difeafed  (late  of  the  intefti- 
nal  tube.  I  am  induced  to  entertain  this  opinion 
from  having  never  been  able  to  difcover,  in  the 
found  fmaJl  inteftines  of  fubje&s  carefully  exami- 
ned in  different  periods  of  life,  the  fmallefl  veflige 
of  fuch  fungous  papilla?,  perforated  with  orifices  ; 
whereas,  on  the  other  hand,  I  have  frequently 
feen,  in  cafes  of  aphtha,  almofl  the  whole  intefti- 
nal  canal  planted  with  countlefs  numbers  of  them, 
partly  (landing  alone,  and  partly  arranged  in 
crouded  duffers.  From  confiderin^  the  forerointr 
circumftances,  I  feel  a  confidence  in  concluding, 
that  none  can  be  accounted  true  muciferous 
glands,  except  thofe  extremely  minute  miliary  bo- 
dies, which,  on  gently  feparating  the  •villous  lining, 
may  be  readily  detected  on  its  averted fur/arc,  but 

cannot, 


<?o  OF  THE  INTESTINES. 

cannot,  without  great  difficulty,  be  diilinguifhed 
on  the  fide  next  to  the  eye. 

§  4*5- 
It  has   been    incontrovertibly    eftablifhed,  not 

only  from  that  well  known  experiment  fir  ft  infli- 
tuted  (if  I  miitake  not)  by  Pechlin,  but  alfo  from 
feveral  others,  that  as  the  ftorr.acb,  fo  in  like 
manner  the  cavity  of  the  fmall  inteflines,  is  fup- 
plied  with  a  conftant  influx  of  a  liquid,  denomi- 
nated, from  the  place  into  which  it  is  cifchargcd, 
inte/iinal  juice.  It  appears  probable  that  this  fluid 
is  fimilar  in  its  nature  to  the  gauric  liqucr,  al- 
though a  more  accurate  inveftigation  of  it  is,  cer- 
tainly as  yet,  a  defideratum  in  phyficlogy  :  nei- 
ther can  I  venture  to  fay  any  thing  decifive  re- 
fpecling  the  quantity  of  this  liquid  fecreted  :  I  am, 
however,  fully  of  opinion,  that  Haller  has  been 
too  profufe  in  his  ellimate,  where  he  alleges, 
that  this  fecretion  amounts  to  eight  pounds  in  the 
fpace  of  twenty-four  hours. 

§  416. 
Further,  it  is  alfo  common  to  the  inteflines  with 
the  ftomach,  to  be  agitated  by  a  fimi/ar,  but  far 
more  lively  and  vigorous  fcrijlaltic  motion^  which, 
In  particular,  while  the  chymous  pulp  is  advancing, 
cfcwsrdp  throws  the  fame  into  gentle  commotion, 

by 


OF  THE  INTESTINES.  6\ 

by  a  wavy  and  progrdftve  ccnftriction,  and  thus 
propels  it  forward  ficm  the  duodenum  towards 
the  great  inredincs.  For  although  we  cannot  ab- 
folutely  deny  the  phenomenon  of  an  anti-periftal- 
tic  commotion,  in  confequence  of  which  the  intef- 
tines  are  fubje&ed  to  a  retrograde  action,  it  mud', 
notwithftanding,  be  acknowledged,  that  this,  in  a 
healthy  fubjecl:,  is  much  feebler  than  the  former, 
that  it  occurs  more  rarely,  and  pofTefks  a  more 
precarious  and  (liort-lived  exigence. 

§  4*7- 

In  confequence  of  the  co-operation  of  thofc 
energetic  caufes,  hitherto  enumerated  (viz.  both 
the  principles  of  ?uotim,  of  which  we  have  jiiil 
fpoken,  and  likewife  the  folvent  and  alterative 
powers  of  the  inquiline  humours  that  are  every 
where  blended  in  abundance  with  the  chyme),  the 
following  remarkable  changes  are  produced  in  this 
heterogeneous  mafs  : — in  the  jejunum  it  exhibits 
the  appearance  of  a  more  liquid  pulp,  poiTeiling  a 
colour  fomewhat  grey,  and  an  odour  flightly  acid  : 
alter  its  entrance  into  the  ileum  it  begins  to  fepa- 
rate  into  two  portions  ;  thefe  are,  /Srft,  the  faces, 
marked  by  a  pale  yellow  colour,  inclining  more 
or  left  towards  a  brown,  and  poffeffing  a  fetid 
odour;  and, fecondlj^  a  white  milk-like  fluid,  de- 
nominated true  chile,  whkh  floats  on  the  furface 
of  the  J         ,  and  is  I  .'  from  them  by  the 


62  OF  THE  INTESTINES. 

a&ioti  of  the  hepatic  liquor  or  bile.  This  chy- 
mous  emulfion,  designated  by  the  name  of  chyle, 
is  defined  to  be  received  by  abforption  into  the 
lacleal  veffcls,  through  which  mazy  tubes  we  will 
accompany  it  farther  in  the  following  feclion  ;  and 
iliall,  in  the  mean  time,  clofe  the  prefent,  by  tra- 
cing, in  as  brief  and  intelligible  a  manner  as  pof- 
fible,  the  route  purfued  by  the  refiduary  faxes. 

§  41S. 

Thefe,  therefore,  after  having  become  more  and 
more  infpiffated,  in  confequence  of  a  tedious  courfe 
through  the  ileum,  are  obliged  at  length  to  pafs 
the  vaive  of  the  colon,  and  thus  enter  the  tratt  of 
the  great  intejlines  ;  for  which  purpofe  the  neigh- 
bouring extremity  of  the  ileum  is  furr.ifh.ed,  and 
lubricated  internally,  by  a  more  copious  quantity 
ef  mucus,  deflined  to  deitroy  the  friction  of  the 
fasces,  and  confequently  facilitate  their  tranfition 
through  the  foregoing  valve. 

§  4I9- 
The  valve  of  the  colon  (denominated  very  juftly 

in   honour  of  its   real  and  illuftrious  difcoverer, 

valvula  FallopiiJ,  is  a  mort  continuation  or  procefs 

of  the  ileum  projecting  into  the  cavity  of  the  great 

intejlinal  portion,  by   uhich  it  is  furrounded  and 

ciofely  embraced  :  the  more  exterior  labia  of  this 

procefs  are  fo  condituted,  by  means  of  a  more 

prominent 


OF  THE  INTESTINES.  63 

prominent  or  extenfive  ruga  of  the  great  Intejliiie^ 
as  to  confifl:  not  only  of  its  internal  and  nervous 
coats  (as  is  the  cafe  with  the  greater  number  of 
fuch  plicae),  but  to  contain  alfo  in  its  compofition 
feme  fibres  from  the  mufcular  coat.  Hence  the 
function  of  this  valve  appears  to  be  twofold,  to 
prevent  the  premature  paflage  of  the  fceces  from 
the  f. nail  into  the  great  interlines.,  and  alfo  to  ob- 
ftruct  their  regurgitation  from  the  latter  into  the 
former. 

§  42o. 
The  great  inteftinnl  portion,  which  in  like  mari- 
ner with  the  fmall,  is  alfo  divided  into  three  fec- 
tions,  begins  from  the  ceecum  (to  which  is  append- 
ed the  'vermiform  proeefs,  a  part  indeed  of  equivo- 
cal ufe  in  the  economy  of  an  adult  iubject),  and 
conftitutes  collectively  a  canal  fo  capacious,  as  to 
admit  the  infpiifated  fasces  to  be  gradually  collected 
and  retained  in  its  cavity,  till  a  convenient  oppor- 
tunity for  their  evacuation. 

§  421. 
As  the  great  is  fuperior  to  the  fmall  portion  of 
the  interlines  in  diameter,  fo  it  lifoewife  exceeds  it 
in  the  thicknefs  and  ftrength  of  its  coats.  The 
mufcular  coat,  in  particular,  poffeflfes  this  peculia- 
rity, that  its  longitudinal  fibres  (if  we  except 
lower  part  of  the  rectum)  are  collected  into  tl 

faiuculi 


($  OF  THE  INTESTINES. 

fafciculi  or  bundles,  called  ligamenta  coll  ;  aud  the 
colon  itfelf  is  thus  divided  into  diftinct  fcgments  of 
a  velicular  or  cyftiform  appearance.  The  internal 
coat  in  the  great,  is  not  of  fuch  a  beautiful  and 
elegantly"  floccofe  appearance  as  in  the  fmall  in- 
teflincs4  but  poffeiTes  a  nearer  refemblance  to  that 
which  inverts  the  cavity  of  the  ftomach. 

§  422- 
The  periflaltic  motion  appears  to  be  lefs  vivid 
and  active  in  the  great,  than  in  the  fmall  inteflines. 
On  the  other  hand,  the  abdominal  pre  (fare  is  con- 
fiderably  greater  on  the  former  than  on  the  latter, 
in  as  much  as  the  whole  colon  is  fubjecled  to  its 
immediate  action  and  influence. 

§  423- 
The  infpiflated  and  hardened  feces  contained  in 
the  large  inteflines,  are  protruded  {lowly  onward, 
till  having  at  length  reached  the  rectum,  they  ex- 
cite, by  their  ftimulus  on  the  internal  furface  of 
that  tube,  a  propennty  to  an  evacuation.  For  the 
purpofe  of  facilitating  this  evacuation,  ample  and 
wife  provifion  is  made,  partly  by  a  defect  or  inter- 
ruption iu  the  tranfverfe  rugae,  but  more  efpeci- 
ally  by  a.  profufe  quantity  of  mucus,  that  lubri- 
cates the  internal  furface  of  the  rectum  near  to  its 
extremity* 

a  The 


OF  THE  ABSORBENT  SYSTEM.  65- 

The  evacuation  of  the  fasces  is,  however,  prin- 
cipally accomplished  by  a  downward  dire£tion  of 
the  abdominal  preffure,  overcoming  the  refiftance 
of  the  coccyx  and  both  the  fphincters,  the  interior 
of  which  is  a  very  fingular  fafcifculus  or  bundle 
of  annular  fibres,  but  the  exterior,  a  genuine  cuta- 
neous mufcle  :  thefe  ends  being  quite  completed, 
there  fucceeds  an  entire  remiffion  of  the  abdominal 
effort,  the  inteftine  is  retracted  by  the  levator  ani 
in  particular,  and  finally  clofed  a^ain  by  the  con- 
traction of  the  fphindters. 


SECT.    XXXIV. 
OF  THE  FUNCTIONS  OF  THE  ABSORBENT  SYSTEM. 

§  4H- 

.  -T  ROM  obfervations  delivered  in  a  for- 
mer fe&ion  it  is  fufficiently  evident,  that  the  chyle, 
which  we  left  in  the  inte/iinum  ileum,  completely 
difen^aged  from  its  fasces,  is  a  compound  of  feve- 
ral  different  humours.  Although  it  be  almoft  li- 
terally impoflible  to  calculate,  with  accuracy  and 
definitude,  the  precife  quantity  of  inquiline  hu- 
mours, fuch  as  faliva,  gaflric  juice,  pancreatic  juice, 
inteflinal  juice,  bile,  &c.  that  is  mixed  and  blended 
vol.  ii.  E  with 


66  OF  THE  ABSORBENT  SYSTEM. 

with  the  chyme,  it  appears,  notwithstanding,  a 
mutter  of  the  higheft  credibility,  that  thefe  feveral 
humours,  taken  collectively,  very  far  exceed,  in 
quantity,  the  other  conftituent  part  of  the  cfy'le, 
which  is  derived  immediately  from  alimentary  fub- 
ftances,  recently  taken  as  nutriment.  Hence  we 
may  derive  a  folution  of  that  problem  in  phyfio- 
logy,  by  what  means  alimentary  matters,  though 
of  the  mofl  different  and  even  oppofite  kinds,  may, 
notwithflanding,  be  converted  into  the  fame  aflimi- 
lized,  homogeneous,  and  milk-like  chyle,  equally 
adapted  to  the  nature,  and  calculated  to  ferve  as 
the  nutriment,  of  animals  ? 

§  4-5- 

The  channels  through  which  the  chyle  rnufl 
flow,  in  its  paffage  from  the  inteflines  jto  the  mafs 
of  blood,  (the  refervoir  deftined  for  its  ultimate  re- 
ception), conflitute  a  part  of  the  abforbent  fyjlem, 
which  we  have  hitherto  mentioned  only  occafion- 
ally,  and  in  a  very  curfory  manner,  but  will  now 
affume  as  the  profeiTed  object  of  our  prefent  at- 
tention. This  fyflem  is  divided  generally  into 
four  parts,  viz.  lacteal  veins ;  lymphatic  veins  ; 
conglobate  glands ;  and  finally,  the  thoracic  duel;, 
each  of  which  fhall  conftkute  a  fubject  of  exclu- 
five  confideration. 

-§426. 


OF  THE  ABSORBENT  SYSTEM.  67 

With  refpect  to  the  nafcent  origin  of  the  lac- 
teals  from  the  inteftines,  there  exilts  fcarccly  a 
doubt,  but  that  this  is  conftituted  by  the  innume- 
rable villi  of  the  internal  inteftinal  coat,  of  which 
we  have  already  fpoken.  It  is,  however,  dill  a 
matter  of  controverfy,  whether  the  lacleals  origi- 
nate immediately  from  thofe  villi  themfelve?,  or 
only  preferve  a  more  diftant  intcrcourfe  and  com- 
munication with  them,  by  means  of  interjacent 
cellular  fubftance.  As  far  as  my  information  has 
extended,  no  one  has  hitherto  been  able,  more 
than  myfelf,  to  trace  the  evanefcent  radicles  of  the 
lacteal  veifels  to  the  villi  themfelves,  with  fuch 
clearnefs  and  definitude,  as  to  difcover  an  imme- 
diate and  unequivocal  connexion  between  the 
parts  ;  on  the  other  hand,  the  lacleals  appear  here 
and  there,  throughout  the  coats  of  the  inuftines, 
to  form  trunks  of  coniiderable  fize,  immediately 
after  their  orgin,  and,  (if  a  conjecture  be  allow- 
able), to  abforb  from  the  cellular  fubftance  of  the 
adjacent  parts,  that  chyle  which  had  been  origi- 
nally taken  up  from  the  cavity  of  the  inreflines  by 
means  of  the  villi  themfelves.  This  phenomenon 
I  think  I  have  frequently  obferved,  in  young  pup- 
pies, into  which  I  had  poured,  according  to  the 
celebrated  experiment  of  Lifter,  a  foluti  m  of  In- 
dian blue,  one  or  two  hours  before  fubje&ing 
them  to  the  operation  of  livs-difleftion. 

E  2  §  427* 


58    OF  THE  ABSORBENT  SYSTEM. 

§  427- 
Thofe  trunks,  of  which  we  have  juft  fpoken, 
frequently  run  the  diflance  of  feveral  inches,  and 
fometimes  even  wind  about  in  angling  or  mean- 
der-like directions,  immediately  under  the  external 
coat  of  the  inteftine,  previoufly  to  their  entrance 
into  the  mefentery. 

§  4^8- 
During  their  paffage  through  the  mefentery, 
thefe  trunks  make  frequent  entrances  into  fmall 
vis/enteric  g/ands,  which  may  be  divided  into  two 
different  feries  or  orders.  Thofe  of  the  firfl  order 
are  fituated  in  the  vicinity  of  the  inteftinal  tube, 
and  referable,  in  their  appearance,  fmall  beans  ly- 
ing feparate  from  each  other.  The  glands  of  the 
other  order,  lie  nearer  to  the  receptacle  of  the 
chyle,  are  fuperior  in  magnitude,  and  planted  in 
collective  clutters. 

§  429- 
Both  the  foregoing  kinds  of  glands  appear  to 
be  in  reality  nothing  elfe,  than  round  compacted 
convolutions  of  the  lacteal  veffels  themfelves,  co- 
vered and  interfperfed  with  an  infinitude  of  minute 
blood-veffels  :  their  deflination  appears  to  be,  to 
retard  the  progreffive  motion  of  the  chyle,  in  or- 
der, perhaps,  that,  by  fuch  delay,  it  may  be  more 
fully  and  perfectly  animalifed  and  matured,  previ- 
oufly 


OF  THE  ABSORBENT  SYSTEM.  69 

oufly  to  its  entrance  into  the  thoracic  duct,  and 
fubfequent  admixture  with  the  circulating  volume 
of  the  blood. 

§  43°- 
It  has  been  propofed  as  a  phyfiological  queflion, 
whether  or  not  the  large,  poffefs  alfo  Ia&eal  veins, 
in  common  with  the  fmall  intcftines  ?  The  affirma- 
tive of  this  has  been  zealcufly  advocated,  and  its 
defence  attempted  by  arguments  drawn  from  the 
influence  and  efficacy  of  fpecific  enemas,  of  ene- 
mas compofed  of  nutrimental  fubftances,  of  ine- 
briating fubftances,  &c.  and  alfo  from  the  follow- 
ing well  known  circumftance,  viz.  that  the  longer 
infpiiTated  fasces  are  retained  in  the  large  portion 
of  the  alimentary  canal,  the  more  indurated  and 
infucculent  they  are  uniformly  found.  But  al- 
though thefe  arguments  do  not  fatisfaclorily  de- 
monftrate  that  any  genuine  chyle  is  abforbed  from 
the  faeces  after  their  tranlition  over  the  valve  of 
Fallopius,  they  furnim,  notwithftanding,  additional 
evidence  in  confirmation  of  that,  which  has  indeed 
been  long  fince  eftabliihed  on  the  teftimony  of 
the  fenfe  of  vifion  itfelf,  namely,  that  the  great  in- 
terlines abound  with  a  fufficiently  plentiful  appa- 
ratus of  lymphatic  veins,  perfectly  fimilar  to  the 
lacttals  both  in  their  ftructure  and  functions  :  in 
teftimony  of  this  entire  ilmilarity,  it  may  be  proper 
to  obferve,  that  when  the  inteftines  are  deftitute 
E  3  of 


7©  OF  THE  ABSORBENT  SYSTEM. 

of  chyle,  the  lacVals  of  the  mefentery  are  then 
eng  iged  in  the  afeforption  of  lymph. 

§   431- 
Another  qucftion,  more  important  and  difficult 

of  folution  than   the  former,  is,  whether  or  not 

the  whole  of  the  chyle,  abforbed  from  the  cavity 

of  the  fmall  inieftines,   be  conveyed  to  the  blood 

through  the  fame  public,  and  royal  route,  as  it  is 

termed,  or  whether  there  do  not  ex  id  certain  fe- 

cret  channels,  through  which  it  may  glide  furrep- 

titioufly  onward,  to  mingle  its  flreamlets  with  the 

general  current  of  circulating  blood  ? 

It  mull  indeed,  be  confeffed,  that  mod:  of  the 
arguments,  by  which  phyfiologifts  have  endea- 
voured to  prove  a  private  abforption  and  convey- 
ance of  chyle  through  the  fanguiferous  veins,  do 
not  appear  to  reft  on  a  very  folid  foundation  : 
thus  the  affenion  of  Ruyfch,  that  on  the  approach 
of  old  age  the  mefenteric  glands  become  fo  indu- 
rated and  conRricted,  as  to  be  rendered  unfit  for 
performing  their  functions,  has  been  long  fmce  re- 
futed, and  it  has,  on  the  other  hand,  been  fatif- 
faclorily  demonftrated  that,  different  affections  of 
thefe  glands,  fuch  as  fwellings,  &c.  very  errone- 
ously pafs  under  the  common  name  of  ob/lruclions, 
while,  at  the  fame  time,  their  veffels  remain  in  a 
ftate  fufneiently  pervious  to  afford  a  very  eafy  en- 
trance 


OF  THE  ABSORBENT  SYSTEM.  71 

trance  and  tranfition  to  injections  of  quick  filver. 
That  well  known  phenomenon,  from  which  it  is 
afcertained,  that  tepid  water,  thrown  into  the  inert 
mefenteric  veins  of  a  dead  fubject,  tranfudes  into 
rhe  cavity  of  the  imeftines,  appears  to  contribute 
but  very  little  towards  the  fatisfactory  elucidation 
of  any  function  of  the  human  body  while  in  a 
living  ftate  ;  much  lefs  can  we  repofe  confidence 
in  the  evidence  derived  from  that  bicrural  and  two 
branched  tube  of  copper,  which  was  invented  by 
Lieberkuhn,  for  the  purpofe  of  confirming  the 
fame  opinion.  As  to  the  aflertion,  that  chyle  has 
been  unequivocally  detected  in  the  red  veins  of 
the  mefentery,  it  appears  to  me  to  (land  in  need 
of  farther  evidence  for  its  unquestionable  confir- 
mation ;  on  the  whole,  I  have  never  yet  been 
convinced,  that  thofe  veins  convey  any  thing  elfe 
than  blood  very  highly  charged  with  phlogifton, 
-deftined  for  the  fecretion  of  bile. 

S  432. 
"Finally,  the  ultimate  trunks  of  the  lacteal  veins, 
(with  certain  other  tubes  very  fimilar  in  appear- 
ance and  function,  which  are  formed  by  the  con- 
fluence of  a  great  number  of  minute  lymphatic  vef- 
fels),  unite  and  conftimte  by  their  junction,  the 
receptacle  or  cijiern  of  the  chyle,  which  is  a  name 
given  by  phyfiolc-gifls  to  the  inferior  and  larger 
E  4  portion 


72     OF  THE  ABSORBENT  SYSTEM. 

portion  of  the  thoracic  duel,  called  alfo  the  duel  of 
Pecquet. 

§  433- 
This  duct  is  a  membranous  canal,  of  a  delicate 
appearance  and  texture,  yet  fufficiently  robuft  and 
ftrong,  more  or  lefs  circuitous  in  its  courfe,  and 
not  unfrequently  fubject  to  very  flriking  diverfities 
W'i  h  regard  to  the  direction  in  which  it  runs,  and 
the  divifions  it  occafionallv  undergoes  :  it  is  equal- 
ly deflitute  of  mufcular  fir-res  and  nerves,  is  fur- 
nifhed  here  and  therewith  fmall  valves,  and,  after 
having  paffed  over  the  left  fubci 'avian  vein,  is  again 
reflected  towards,  and  finally  inferted  into,  the 
fame,  and,  at  the  very  point  of  infertion,  has  its 
entrance  guarded  by  a  valve  of  a  peculiar  ftruc- 
ture. 

§  434- 
The  powers  which  produce  and  continue  the 
onward  motion  of  the  chyle,  both  in  the  lacteal 
veins,  and  through  the  thoracic  duel,  are  to  be 
attributed,  indeed,  principally  to  the  contractility 
of  thefe  veifels  themfelves,  but,  in  part  alfo,  to 
the  valves  with  which  they  are  furniftied,  to  a 
propulfive  vis  a  tergo,  and  to  the  uninterrupted 
pulfation  of  neighbouring  arteries, 

§  435- 


OF  THE  ABSORBENT  SYSTEM.  73 

§  435- 

It  appears  probable,  that  the  principal  deitina- 
tion  of  the  valve,  which  is  fixed,  as  has  been  al- 
ready obferved,  in  the  entrance  of  the  chyliferous 
duel:  into  the  fubclavian  vein,  is  not  fo  much  to 
obflruct.  the  lateral  paffage  of  blood  into  this  duct, 
as  to  regulate  the  neceffary  difcharge  of  chyle  in- 
to the  vein,  and  prevent  its  admiflion  in  any  other 
manner  than  by  a  flow  and  gradual  flillicidium. 

By  this  means,  adequate  provifion  is  made 
againft  the  fimultaneous  entrance  of  too  large  a 
quantity  of  recent  chyle,  into  the  mafs  of  blood. 
Such  an  exceflive  influx  of  this  crude  fluid  would 
necefiarily  ftimulate  the  parietes  of  the  heart  to  ex- 
ertions too  violent  and  laborious,  and  would  be 
blended  and  aflimilated  by  the  fame,  with  the  ut- 
moft  difficulty,  and  in  an  imperfect  manner ;  that 
this  would  be  the  refulr,  we  judge  from  the  nature 
of  recent  chyle,  which  is  a  compound  of  hetero- 
geneous elements,  derived  net  only  from  the  pri- 
ma via,  by  means  of  the  lacleal,  but  alfo  from 
all  the  other  parts  of  the  body,  through  the  ave- 
nues of  the  lymphatic  vejfels. 

§   436. 
The  lymphatic  veins  the.nfelves,  which  confti- 
tute  a  third  part  of  the  abforbent  fyftem,  and  bear 

a  very 


74  OF  THE  ABSORBENT  SYSTEM. 

a  very  clofe  refemblancc  to  the  la&eals,  both  in 
flruelure  and  in  function,  are  fo  considerable,  in 
point  of  extenfion,  as  to  pervade,  perhaps,  every 
part  of  the  human  body  ;  but  originate,  in  parti- 
cular, from  the  common  external  integuments, 
from  the  pleura,  the  peritoneum,  and  vifcera, 
contained  in  the  thorax  and  abdomen. 

S  437- 
The  manner  in  which  they  arife,  is  fimilar  to 

the  origin  of  the  la&eals  from  the  inteitines,  of 
which  we  have  already  fpoken.  Thus  each  radi- 
cle of  each  lymphatic  veflel,  is  deftined  to  abforb 
from  a  neighbouring  portion  of  cellular  membrane, 
(as  from  a  territory  of  its  own),  the  moifture  it 
contains,  and  propel  it  onward  to  the  general  cif- 
tern  of  the  chyle. 

§  43S. 
Thefe  lymphatic  vejfels  are  furnifhed  in  their 
courfe,  fomctimes  more  frequently,  fometimes 
more  rarely,  with  valves  fituated  in  biga  or  pairs. 
By  far  the  greater  part  of  them  enter  conglobate 
glands  -y  thofe  in  the  vicinity  of  each  other  fre- 
quently anaftomofe ;  and  fuch  of  them  as  over- 
fpread  the  furface  of  certain  vifcera,  as  that  of  the 
lungs,  the  liver,  &c.  form  exquiiitely  elegant  reti- 
cular expanfions. 

§  439- 


OF  THE  ABSORBENT  SYSTEM.  75 

§  439- 
To  pafs  filently  over  certain  other  aids,  fuffici- 
ently  evident  from  former  obfervations,  the  func- 
tion of  the  lymphatics  is  greatly  promoted  by  their 
remarkable  contractility,  and  the  Jlrength  of  their 
delicate  coats,  which  is  fufficient,  in  proceffes  for 
anatomical  preparations,  to  refill:  the  prefiure  from 
a  ponderous  column  of  quick  filver  :  this  function 
is  a!fo  further  aided,  efpecially  in  the  joints,  by 
mufcular  motion,  in  confequence  of  which,  the 
lymphatics  being  compreffed  and  clofely  embraced 
on  all  fides,  have  their  tone  remarkably  aug- 
mented. 

§  44°- 
With  refpect  to  the  terminations  of  the  lym- 
phatics, various  controverfies  have  lately  exifled 
among  phyfiological  writers.  Thus,  while  fome 
contend,  that  all  thofe  veflels  unite  in  the  thoracic 
duel:,  (in  like  manner  as  the  fanguiferous  veins 
unite  in  the  venae  cavas),  others,  on  the  contrary, 
exempt  from  this  general  confluence,  at  lead  the 
lymphatics  of  the  right  arm,  and  right  fide  of  the 
neck,  which  they  allege  are  not  inferted  into  the 
fame  duct,  but  into  the  right  fubclavian  vein : 
others  again  affert  that  in  the  conglobate  glands, 
the  lymphatics  communicate  immediately  with  fan- 
guiferous veins ;  and  laftly,  others  maintain  (not 
indeed  without  an  appearance  of  probability)  that 

certain 


76    OF  THE  ABSORBENT  SYSTEM. 

certain  lymphatic  vcffcls  *,  actually  cxift,  which 
form  a  direct  and  free  communication  between  the 
inteilinal  tube  and  uropoietic  organs. 

5  441- 
Seeing  therefore,  the  lymphatic  vefTds  are 
extended  far  and  wide  throughout  almoft  the 
whole  fyftem,  and,  cfpecially,  in  us  much  as  an 
immenfe  profundi  of  them  originate  on  the  cuta- 
neous furface  of  the  body,  and  may  confequently 
abforb  fuch  fluids  as  arc  applied  from  without,  it 
is  fufficiently  evident,  that  the  lymph,  when  re- 
cently abforbed,  muff,  be,  indeed,  a  liquid  eompo- 
fitipn  extremely  heterogeneous  and  diverfified  as 

*  For  a  great  number  of  truly  important  cbfervations 
and  highly  interefling  {peculations  on  this  fubjecT,  the  reader 
is  referred  to  a  fhori  treatife,  written  by  Charles  Darwin, 
"  On  the  retrograde  motion  of  the  lymphatics,"  and  pub- 
lifhed  at  Litchfield  in  the  year  1780,  a  confiderable  period 
of  time  after  the  premature  death  of  its  ingenious  author. 
This  young  philofopher  and  phyiician  appears  to  have  been 
peculiarly  formed  by  nature,  and  happily  fmiflied  by  edu- 
cation, to  fhed  unequivocal  light  on  fubjefts  of  a  dark  and 
difficult  nature  in  the  fcience  of  medicine.  He  experimented 
with  accuracy  and  dsfinitude,  he  obferved  with  the  utmoft 
attention,  and  he  fpeculated  with  the  higheft  ingenuity  and 
force.  Unhappily  for  the  healing  art,  and  (perhaps  I  may 
add)  for  fcler.ee  in  all  its  aarious  branches,  this  amiable 
young  philofopher  was  haftily  fummoned  away,  ere  yet  his 
mind  was  perfectly  expanded,  or  his  plenitude  of  merit 
announced  to  the  wo;  Id. 

to 


OF  THE  ABSORBENT  SYSTEM.     77 

to  its  nature  and  elementary  parts  :  this  diverfity 
is  fully  afcenained  and  eftabltfhed,  by  a  more 
careful  and  accurate  examination  of  dead  fubjecls, 
where,  for  inftance,  the  liquid  contained  in  the 
abforbents  of  the  liver  and  fpleen,  appears  to  be 
evidently  different  from  that  difcovered  in  thofe 
which  run  to  the  uterus. 

§  442- 
Of  the  conglobate  glands,  (which  conftitute  the 
laft  branch  of  the  lymphatic  fyftem),  the  prin- 
cipal ufe  and  defoliation  appear  to  be,  to  aflimi- 
late  to  the  animal  nature  this  fubtle  and  hetero- 
geneous fluid,  efpecially  that  portion  of  it  which 
is  abforbed  by  the  lymphatics  of  the  fkin  :  this 
afTimilation  they  accomplifh  by  retarding  and  in 
fome  meafure'obftrucrjng  the  motion  of  the  lymph, 
and  perhaps  alfo  by  the  addition  of  a  new  fluid, 
derived  from  the  minute  arteries,  with  which  they 
very  plentifully  abound.  Hence  a  wife  and  ade- 
quate provifion  is  made,  to  prevent  the  humours, 
while  in  too  crude  a  ftate,  from  effecting  a  prema- 
ture mixture  with  the  blood,  and  thus  the  heart 
is  guarded  in  perfect  fecurity  from  their  noxious 
imprefiions. 

5  443- 
With  refpect  to  thofe  other  glands  of  the  fame 
nature,  which  are  niinutelv  difprqad  throughout 

by 


78  OF  SANGUIFICATION. 

by  far  the  greater  part  of  the  fyftem,  and  planted 
here  and  there  in  collected  clutters,  as  in  the 
groin,  beneath  the  axilla,  &x.  they  bear,  in  every 
refpecl,  the  mod  perfect  refemblance  to  the  me- 
fenteric  glands,  of  which  we  have  already  fpoken  ; 
like  them  they  are  compofed,  in  a  great  meafure, 
of  the  mazy  convolutions  of  abforbent  veins ;  like 
them  they  are  furnifhed  with  a  vaft  profufion  of 
minute  blood  veffels ;  and  finally,  they  are  fubject 
to  be  readily  invaded  by  the  fame  difeafes  that 
attack  the  glands  of  the  mefentery. 


SECT.    XXXV. 
OF    SANGUIFICATION. 

§   444- 

-T  is  fcarcely  neceffary  to  obferve,  that 
by  the  term  fanguification,  we  mean  the  affimila- 
tion  of  chyle  to  blood,  and  the  conftant  and  uni- 
form restitution  made  by  means  of  the  former,  for 
the  equally  conftant  and  uniform  lofs  which  is  fuf- 
tained  by  the  latter. 

§  445*- 
For  on  this  principle  depends  that  divifion  of  all 
the  humours  of  our  body,  into  the  three  clafles 

(§4- 


OF  SANGUIFICATION.  19 

(§  4'  5')  °^  crude,  fanguineous,  and  fecreted ;  viz. 
that  the  middle  clafs  embrace  the  whole  circula- 
ting volume  of  blood,  from  which  the  different  fe- 
creted  humours  are  derived  in  conflant  ftreamlets, 
and  to  which  the  countlefs  channels  of  the  abfor- 
bent  fyftem  convey  their  chyle,  and  the  infinitude 
of  lymphatic  tubes  return  their  abforbed  fluids  in 
currents  equally  conftanr  and  uniform. 

§  446. 
Seeing  the  blood  is  an  animal  humour  of  fo  very 
fingular  and  exclufive  a  kind,  as  to  be  wholly  dif- 
fimilar  to  every  other  fluid  yet  difcovered  in  any 
department  of  nature,  it  is  a  proportion  fufficiently 
felf-evident,  that  there  mud  be  a  variety  of  afUfl:- 
ant  powers  which  contribute,  by  their  joint  co- 
operation, to  incorporate  and  affimilize  with  the 
blood,  the  heterogeneous  and  adventitious  hu- 
mours, which  it  is  conftantly  deriving  from  the 
thoracic  duel:. 

§  447- 
The  procefs  of  fanguification  we  may  confider, 
then,  as  firlt  commencing  under  the  action  and 
influence  of  thofe  mazy  circumvolutions  (frequent- 
ly fpoken  of  already),  which  both  the  lacteal  and 
lymphatic  veins  exhibit  occafionally  in  their  courfes 
(more  efpecially  in  the  mefenteric  and  other  con- 
globate 


80  OF  SANGUIFICATION*. 

globate  glands),  and  which  are,  at  the  fame  time, 
furn idled  with  coufijerable  quantities  of  what  may 
be  called  animal  and  inquiline  contagion, 

§  448- 
It  is  neceffary  further  to  confider,  that  a  great 
part  of  the  lymph,  which  enters  the  fubclavian 
vein  (after  having  firft  effe&ed  a  mixture  with  the 
inteftinal  chyle  in  the  thoracic  du&),  is  derived 
from  the  interior  recedes  of  the  vifcera  and  other 
foft  parts  of  the  body,  and  was  formerly  fecreted 
from  the  blood  itfelf ;  from  whence  it  necefLrily 
follows,  that  fuch  portion  of  the  lymphatic  fluid 
mud:  doubtlefs  poflefs,  already,  the  animal  nature 
entire,  and  be  very  readily  mlfcible  with  the  mafs 
of  blood  to  which  it  is  returned. 

§  449- 
To  thcfe  wre  may  add  another  circumdance,  of 
which  we  fpoke  on  a  former  occafion,  naniely, 
the  dow  and  dillicidious  tranfition  of  the  chyle  into 
its  refervoir,  the  blood — that  fluid  not  being  ad- 
mitted to  pafs  through  the  ultimate  valve  of  the 
thoracic  du&  into  the  fubclavian  vein,  in  any 
other  manner  than  by  drops,  in  order  that  thofe 
minute  portions  may,  by  this  means,  be  more  inti- 
mately mixed  and  incorporated  with  the  circu- 


lating blood. 


§  45°- 


OF  SANGUIFICATION.  81 

450 
The  internal  ftru&ure  of  the  heart  itfelf  appears 
alfo  to  contribute,  not  a  little,  towards  the  im- 
portant procefs  of  fanguification.  Thns,  by  means 
of  thofe  aftonifliing  mufcular  papilla?,  with  which 
the  ventricles  of  the  heart  are  plentifully  fur- 
nifhed,  the  blood  and  chyle  (having  recently  met 
together),  are  thoroughly  agitated,  and  brought 
into  a  ftate  of  more  intimate  combination. 

§   451- 
That  the  lungs,  receiving  the  blood,   recently 

impregnated  with  chyle,  perform,  by  the  fun&ion 

of  refpiration,  an   important  part  in  the  farther 

afiimilation  of  this  crude  fluid,  will  appear  fuffici- 

ently  evident  to  any  one  who  confiders  the  aflo- 

mining  vafcular  ftru£hire  of  thefe  vifcera  (§  1  ?6.) 

in  conjunction  with  the  equable  alternate  motion 

to  which  they  are  perpetually  fubje&ed,   during 

the  continuance  of  human  life. 

§  45 2- 
The  remaining  part  of  the  procefs  of  fanguifica- 
tion  is  finally  completed  by  the  more  exten five 
circuitous  journey  of  the  blood  throughout  the 
whole  body,  and  by  thofe  powers  which  con- 
tribute towards  the  continuance  of  the  fame, 
more  cfpecially  mufcular  motion,  Sec. 

vol.  11.  F  §  453. 


Si  OF  SANGUIFICATION. 

§  453- 
But  although  potent   provifion  be  made,  by 
fuch  powerful  and  diverfified  apparatus,  for  blend- 
ing and  intimately  incorporating  the  chyle  with 
the  blood,  it  appears,  notwithftanding,  that  there 
exifts  a  certain  fimilarity  between  the  condiment 
parts  of  thofe  two  fluids.     It  is  very  commonly 
aflerted,  that  a  great  many  hours  mud  elapfe  be- 
fore the  chyle  can  be  completely  diverted  of  its 
own  milky  colour,  and  perfectly  affimilated  to  that 
of  the  crimfon  fluid  into  which  it  is  deftined  to  be 
converted  :  in  teftimony  of  the  truth  of  this  afler- 
tion,  medical  philofophers  ufually  adduce  (befides 
other  arguments)  the  following  fingular  patholo- 
gical phenomenon,  namely,  that  feveral  hours  after 
the  clofe  of  digeftion,  genuine  chyle  has  been  fre- 
quently obferved  to  flow  from  an  orifice  made  ia 
a  vein  of  the  human  body :   this  phenomenon  I 
have  indeed  had  an  opportunity  of  obferving  rny- 
felf ;  but  it  was  at  the  fame  time  extremely  evi- 
dent, that  the  blood  was  then  highly  charged  with 
phlogifton    (a    condition    of  this   fluid   very  un- 
friendly to  the  regular  aflimilation  of  chyle),  fo 
that   from   hence   fcarcely  any   inference   can  be 
drawn  relative  to  the  healthy  ft  ate  of  the  fyftem, 
which  is  alone  the  exclufive  fubjeft  of  the  fcience 
&f  physiology. 

SECT. 


Of  nutrition*  &3 

sect:   xxxvi. 

OF    NUTRITION. 

§  454* 

xJeSIDES  that  funflion  (which  we  at- 
tributed to  the  blood  in  a  former  fedYion)  of  dif- 
tributing  the  element  ofjire  throughout  the  whole 
body,  and  in  its  place  wafting  that  of  fhlogijlon 
back  to  the  lungs,  two  of  its  primary  and  leading 
offices  appear  to  be,  to  convey  to  the  body  nou- 
rifhir.ent,  and  to  rhe  fecretory  organs  the  matter 
of  thofe  peculiar  fluids  which  they  are  feverally 
deft  ned  to  extract.  Of  this  twofold  function  we 
wi  I  next  treat ;  and  firjl  of  the  function  of  nu* 
trition. 

§  455- 
Nutrition  is  the  fupreme  privilege  of  nature. 
It  is  a  common  and  leading  prerogative  of  all  or- 
ganized bodies,  whether  animal  or  vegetable,  by 
which  they  are  inftamly  difcovered,  on  firft  view, 
to  furpafs,  in  an  immeafureable  degree,  all  ma- 
chines and  automatons  conftru&ed  by  human  ar- 
tifice :  becaufe  on  none  of  thefe  latter  has  any 
artift  ever  been  able  to  confer  a  power  (I  will  not 
fay  of  actual  growth,  of  progreffing  toward  matu- 
rity, and  of  acquiring  gradually  higher  and  higher 
F  2  degree** 


$4  OF  NUTRITION. 

degrees  of  perfection  J,  but  not  even  of  preferring 
themfelves  in  a  ftate  of  Jlationary  exiftence  by  their 
own  inherent  powers,  nor  of  repairing  the  gradual 
lofles  to  which  they  are  fubjecled  by  attrition,  by 
incidental  cafualties,  &c. 

§  45& 

Nutrition  is  that  faculty  of  our  bodies,  on  which 
all  the  fublime  and  aftonifhing  functions  of  our  na- 
ture depend.  By  means  of  this  faculty  we  increafe 
in  magnitude  from  the  earlieft  dawnings  of  our 
exiftence,  we  advance  through  the  expanding 
period  of  youth,  and  finally  arrive  at  our  acme, 
or  point  of  complete  maturity.  It  is  alfo  through 
the  inftrumentality  of  this  fame  faculty  that  a  com- 
petent remedy  is  applied,  and  fufficient  reftitution 
made,  for  that  uniform  wade  and  lofs  of  the  body, 
by  which  (while  in  a  living  (late)  it  deftroys  and 
in  fome  meafure  cenfumes  itfelf,  by  its  own  necef- 
fary  action. 

§  457- 
With  refpect  to  the  nature  and  mode  of  this 
zuajiing  or  lofs,  various  controverfies  have  exifted 
among  phyfiologifts.  The  more  immediate  point 
of  difputation  has  been,  whether  fuch  wafle  occurs 
in  the  folid  parts  of  our  bodies,  or  whether  it  be 
not  more  probable,  that  thofe  parts,  when  once 
formed  and  completed,  remain  ftationary,  without 

being 


OF  NUTRITION.  g5 

being  fubjecl:  either  to  vitiation  or  change  ?  which 
latter  is  indeed  an  opinion  embraced  and  taught 
by  feveral  characters  of  the  utmoft:  acumen  and 
ingenuity. 

§  45  & 
With  refpecl  to  fome  particular  folid  parts  of 
die  body,  fuch,  for  example,  as  the  epidermis, 
the  nails,  &c.  there  exifts  indeed  not  a  madow  of 
doubt,  but  that  they  are  gradually  deftroyed  and 
again  repaired  ;  and  with  regard  to  the  deftru&ion 
or  wafte  and  fubfequcnt  reparation  of  the  bones 
themfelves,  the  teftimony  will  appear  equally  plain 
and  conelufive,  to  any  one  who  may  confider  with 
attention  the  refult  of  the  well  known  experiments 
made  by  feeding  warm-blooded  animals,  for  fome 
time,  on  the  root  of  the  rubia  tinfiorum,  or  who 
may  take  the  further  trouble  of  contemplating 
attentively  the  phenomena  exhibited  by  certain 
large  plain  bones,  efpecially  thofe  of  the  cranium, 
which  in  extreme  old  age  become  remarkably 
attenuated,  or  diminiihed  in  thickncfs,  in  confe- 
rence of  the  fcanty  nourifliment  with  which  they 
are  fupplied  at  that  period  of  life. 

S  45°- 

Upon  the  whole,  if  I  be  capable  of  judging 

rightly,   thofe  folid  parts  appear  to  be  not  only 

gradually  confumed,  and  again  repaired,  by  the 

f  3  faculty 


86  OF  NUTRITION. 

faculty  of  nutrition,  but  poffefs  alfo  a  vis  repro- 
ducliva,  or  power  of  re-produ&ion.  This  latter 
is  indeed  a  furprifmg  faculty,  deflined  not  only 
to  make  reftitution  for  the  uniform  removal  of 
minute  atoms  by  the  neceflary  action  of  the  animal 
economy,  but  alfo  to  repair  the  incidental  lofs  of 
larger  parts  (fuffered  in  confequence  of  external 
injuries,  wounds,  &c),  by  a  perfeft  restoration  of 
the  fubftance  of  which  the  body  has  been  thus 
forcibly  deprived.  That  fuch  a  power  does  un- 
equivocally refide  in  the  bones,  and  a  few  other 
parts,  of  which  we  have  jufl  fpoken,  is  with  me 
too  well  afcertained  and  fubftantiatcd  to  admit  of 
a  doubt* 

§  460. 

But  on  the  other  hand,  from  a  variety  of  obfer- 
vations  and  experiments  which  I  have  made  both 
on  man  and  other  warm-blooded  animals,  this 
power  of  reproduclion  appears  to  refide  in  fcarcely 
any  other  folid  parts  of  the  body  than  fuch  as  are 
endowed  with  contraclility  alone ',  without  poffcfj'ing 
at  the  fame  time  any  of  the  other  vital  energies, 
fuch  as  irritability,  fenfibility,  or  finally,  fpecific  lift, 

§   461. 

Of  thofe  parts  of  the  fyftem  therefore  (which 
poiTefs  the  more  exalted  kinds  of  vital  energy), 
;he  flaminal  bafis  appears  to  me  to  confift  oi  a  pe- 
rennial 


OF  NUTRITION.  S7 

rennlal  parenchyma,  which  is  fubjeft  neither  to 
genuine  mutation  nor  decay,  but  only  liable  to 
certain  viciffitudes  in  point  of  bulk,  that  are  pro- 
duced in  the  following  manner,  namely,  when 
the  procefs  of  nutrition  is  conducted  with  fuffi- 
cient  activity  and  vigour,  the  cellular  interfaces  of 
the  parenchyma, being  uniformly  filled  with  the  rich 
and  plallic  lymph  of  the  blood,  are,  of  courfe,  dif- 
tended,  and  the  parenchyma  neceiTarily  enlarged  -9 
but  when,  on  the  other  hand,  nutrition  goes  on 
lefs  favourably,  thefe  fame  interfaces,  being  in  a 
great  meafure  deprived  of  this  nutritious  lymph, 
fall  into  a  ft  ate  of  collapfe,  and  the  parts  become 
eonfequently  diminiihed  in  fize. 

§  462. 

With  refpecr.  to  this  plaftic  lymph  (of  the  dig- 
nity and  importance  of  which  we  have  fpoken 
fully  on  a  former  occafion),  as  it  alTumes  with 
great  facility  the  appearance  and  nature  of  genuine 
cellular  membrane,  fo  it  appears  to  conftitute  ge- 
nerally the  principal  nutritious  matter  of  the 
whole  fyftem,  and  is  conveyed  to  every  part  of  the 
body  by  means  of  that  infinitude  of  minute  blood- 
velTels,  to  which  we  have  fo  often  called  the 
leader's  attention. 

F  4  §  463. 


SS  OF  NUTRITION. 

§  463- 

During  the  time  of  the  body's  advancement  in 
growth,  it  appears  to  poflefs  certain  peculiar  or 
fpecific  powers,  by  the  aid  of  which  the  lymph, 
being  depofited  from  the  evanefcent  extremities 
of  the  fanguiferous  vefTels,  into  the  furrounding 
cellular  membrane,  is  duly  arranged,  and  com- 
pletely aflimilated  to  each  particular  portion,  and 
kind  of  parenchyma.  To  the  head  of  thefe  fpecific 
powers,  mufl  we  in  part  refer  that  particular  law 
of  affinity,  by  means  of  wThich  the  partes  fimilares 
of  the  fyftem  attract  and  appropriate  to  themfelves, 
the  homogeneous  elements  of  the  nutritious  lymph, 
more  efpecially  fuch  of  them,  as  poflefs  reciprocal 
and  kindred  propenfities ;  and  to  the  fame  head 
may  We  alfo  in  part  refer  that  nlfas  formativus,  of 
which  we  v/ill  have  occafion  to  fpeak  more  fully 
hereafter,  and  to  which  mud  be  attributed,  the 
jufl  and  fpecific  application  of  the  rude,  and  hi- 
therto formlefs,  elementary  mat<:er?  and  its  fubfe- 
qisent  organifation  and  arrangement  into  the  form 
and  figure  of  its  peculiar  deflination. 

§  464. 
It  is,  I  prefume,  from  the  joint  co-operation  of 
both  the  preceding  powers,  that  we  miift  princi- 
pally derive  the  nutrition  of  thofe  parts   of  the 
body,  which  are  not  proximately  fupplied  with  any 

bipod 


OF  NUTRITION.  89 

"blood  veffels  at  all ;  fuch  as  the  nails,  hairs,  &c. 
and  which  are,  notwithstanding,  generated  at  firfl, 
by  a  very  powerful  and  truly  infallible  nifus  or  ex- 
ertion, are  afterwards  advanced  in  magnitude,  and 
regularly  fupported  by  nutriment  throughout  the 
whole  of  life,  and,  finally,  if  by  accident  removed, 
are  again  readily  reftored  by  the  adoniihing 
efforts  of  the  vis  reproduclroa. 

§  465- 
Although  the  preceding  appears  to  be  a  general 
breviate  account  of  the  prccefs  cf  nutrition,  yet, 
on  the  other  hand,  it  is  evident  that  there  exifts, 
in  different  individuals,  a  great  many  varieties, 
with  regard  to  the  degrees  and  modes  in  which 
this  function  is  difcharged.  Thus,  for  example, 
in  proportion  as  a  more  lax  or  more  clofe  appofition 
and  unior.  of  the  nutritious  matter  are  effected,  the 
texture  of  the  parts  themfclves  is  rendered  more 
denfe  or  delicate,  and  hence  alfo  feems  to  origi- 
nate the  difference  between  the  fpecific  weight  cf 
human  bodies  j  in  which  refpeft  it  is  well  known, 
not  only  that  man  differs  from  man,  but  even 
nation  from  nation :  in  tedimony  of  this  truth  it 
may  be  fufBcient  to  adduce  even  a  folitary  example 
from  among  certain  northern  tribes,  namely,  the 
Jukutas,  the  Buratse,  Sec.  people  highly  con.fpi- 
cuous  on  account  of  the  remarkable  and  truly  fin- 
gtilar  levity  of  their  Jjpdies. 

SECT, 


9®  OF  SECRETION, 

SECT.   XXXVII. 
OF    SECRETION. 

-DESIDES  thofe  juices  deflined  for 
the  important  procefs  of  nutrition,  there  are  alfo 
in  the  animal  fyftem  other  humours,  of  a  very 
different  order  and  character,  which  are  extracted 
for  various  purpofes  from  the  exuberant  fountain 
of  the  blood.  Thefe  humours  owe  their  exis- 
tence to  the  procefs  of  fecretion,  than  which  no 
function  is  lefs  underftood  by  phyfiologifts ;  a 
truth  mentioned  as  a  fubjecl:  of  juft  regret,  both 
by  the  immortal  Haller  and  other  preceding 
writers. 

§  467- 

The  fecreted  humours,  appear,  in  one  point  of 
view,  to  be  fo  extremely  diverfified  in  their  na- 
tures, and,  in  another,  to  bear  fo  ftriking  an  affi- 
nity to  each  ether,  that  it  is  not  poffible  to  reduce 
them  to  any,  fave  highly  arbitrary,  clajfes.  If, 
however,  in  treating  of  thefe  humours,  we  found 
our  divifions  of  them  on  the  lefs  and  greater 
changes  to  which  their  elementary  parts,  (con- 
tained 


OF  SECRETION.  t?i 

tained  in  the  mafs  of  blood),  are  fubjected  in  the 
fecretory  organs,  they  may  be  aptly  enough  enu- 
merated in  the  following  order. 

Firft,  the  milk,  a  fluid  which  we  think  proper 
to  place  at  the  head  of  our  cenfus  or  enumeration, 
becaufe  it  may  be  confidered,  in  fome  meafure,  as 
renovated  chyle,  and  appears  to  be  fecreted,  by 
the  moft  funpie  procefs,  from  the  blood,  to  which 
die  chyle  had  been  recently  united. 

Secondly,  the  aqueous  fluids  ;  fuch,  for  exam- 
ple, as  the  humours  of  the  eye,  and  the  tears  : 
to  the  fame  head  mufl  we  refer  in  like  manner, 
the  fweat ;  and  alfo,  (if  our  opinion  be  not  un- 
founded), that  halitus  which  is  contained  gene- 
rally in  the  interfaces  of  the  cellular  membrane, 
as  well  as  in  the  cavities  of  the  thorax  and  abdo- 
men i  this  vapour  appears  to  differ  but  very  little 
either  from  the  liquor  of  the  pericardium,  or  from 
that  fubtle  halitus  by  which  the  ventricles  of  the 
brain,  and  the  pituitary  flnufes  of  the  cranium  are 
preferved  in  a  (late  of  perpetual  humidity. 

Under  the  fame  head  of  aqueous  fluids,  it  is 
liktwife  common  to  arrange  the  urine,  although 
this  is  doubtlefs  a  liquid  poflcfled  of  fome  fingu- 
Jarly  finking  and  peculiar  properties. 


Cf 


f%  OF  SECRETION. 

Of  a  Iefs  compound  nature  are  the  fativarj 
humours,  which,  in  office,  are  fubfervient  to  maf- 
tication,  to  digeftion,  and  to  cbyliikation. 

Thirdly,  the  tnucagenous  fluids,  which  inveft 
and  lubricate  the  cavities  of  mod  of  the  vifcera, 
that  are  deflined  to  the  performance  of  the  natural 
and  genital  functions,  and  alfo  the  internal  furfaces 
of  all  the  aerial  avenues  belonging  to  the  fyflem, 
fuch  as  the  nares,  the  larynx,  and  the  a/pent 
artcria* 

Of  a  nature  not  widely  different  from  the  fore- 
going, is  that  portion  of  mucus  which  covers  the 
internal  fegment  of  the  eyeball  j  as  well  as  that 
which  is  fpread  immediately  beneath  the  epi- 
dermis. 

Fourthly,  the  adipofe  humours  are,  in  particular, 
(befides  the  common  fat  itfelf),  the  medulla  of 
the  bones,  and  the  fmegma  or  oily  covering  of  the 
ikin,  to  which  may  be  added  the  cerumen  aurlum, 
or  waxlike  fubftance  inverting  the  external  ave- 
nues of  the  ears. 

Of  a  nature  nearly  related  to  the  foregoing,  is 
that  un&uous  fecretion,  fo  evident  on  the  glans 
penis  of  the  male,  and  about  the  rima  or  os  exter- 
numy  in  the  genital  organs  of  the  female. 

ynder 


OF  SECRETION.  93 

Under  the  fame  clafs  may  we  alfo  arrange  that 
oily  fubftance,  with  which  the  glands  of  Meibo- 
mius  furnifh  and  anoint  the  eyelids. 

Fifthly,  what  are  commonly  denominated  by 
phyfiologifts  gelatinous  fluids,  examples  of  which 
we  have  in  the  liquor  amnii,  and  ur.guen  of  the 
joints.  Reflecting  the  nature  of  thefe  fluids, 
however,  we  are  not  yet  pofleffed  of  a  fuflicient 
number  of  well  authenticated'  facts  to  give  birth 
to  unequivocal  and  fatisfactory  conclufions:  a 
fimilar  obfervation  may  alfo  be  made,  refpe&ing 
that  uninveftigated  and  anonymous  humour,  which 
the  female  uterus  difcharges  during  the  ardent 
glow  of  the  venereal  orgafm. 

We  remain  alfo  as  yet,  in  a  ftate  cf  equal  un- 
certainty refpe£ting  the  nature  of  that  fluid,  which 
is  lodged,  during  the  firfl  months  after  conception, 
between  the  chorion  and  amnios ;  of  that  which 
is  contained  in  the  umbilical  vc/icula  or  pQv.ch  of 
the  embryo  in  its  tenderer!:  ftate  ;  and  alfo  of  that 
which  is  interpofed  between  the  three  veiTcls  tha: 
conftitute  the  umbilical  cord. 

The  liquid  enclofed  in  the  "ueficttfts  grajfiafia  of 
the  female  ovary,  and  alfo  the  liquor  of  the  prof- 
tare  gland,  appear  to  be  of  a  irvhy  ferffls  or  albu* 
?nhwu;  nature* 


94  OF  SECRETION. 

Sixthlly,  the  male  feme  n  appears  to  be  a  hiimour 
io  remarkably  lingular  in  its  nature,  as  not  to 
admit  of  clarification,  nor  even  of  comparifon^ 
with  any  other. 

And  laftly,  with  regard  to  the  bile,  there  is 
equal  room  for  the  admiiTion  of  a  fimilar  obfer- 
vation. 

§  45S. 

That  the  foregoing  fecreted  humours,  fo  ex«- 
tremely  diverfified  in  their  natures  and  habits,  can 
neither  be  derived  from  the  mafs  of  blood  by  the 
fame  individual  procefs,  nor  by  organs  of  the  fame 
kind,  is  a  propofition  too  felf-evident  to  (land  in 
need  of,  or  indeed  leave  room  for,  any  farther 
confirmation.  Among  thefe  humours,  there  ob- 
vioufly  exifts  this  memorable  variety,  namely,  that 
while  fome  of  them  are  fecreted  and  conveyed 
from  the  blood  through  a  fljortcr  route,  others 
again,  are  more  elaborately  prepared,  by  being 
carried  onward  through  tubes  of  greater  longitu- 
dinal extenfion. 

§  469. 

Of  all  the  modes  of  fecretion,  that  mud  doubt- 
Iefs  be  confidered  as  the  moft  fimple,  in  which  the 
fecreted  humour  appears  to  tranfude  immediately 
through  the  coats  of  the  arteries,  by  what  phyfi- 

ologifts 


OF  SECRETION,  $| 

elogifts  call  diapedefis.  Tnftances  of  this  mode  we 
have  in  the  fecretion  of  the  fat,  and  of  the  medulla 
refiding  in  the  bones,  &c. ;  and,  finally,  it  appears 
to  be  by  a  modification  of  the  fecretory  procefs, 
not  greatly  diflimilar  to  the  foregoing,  that  the 
gaftric  liquor,  the  inteftinal  liquor,  &c.  are  pre- 
pared and  difcharged  into  the  cavities  of  their 
refpe&ive  vifcera. 

§  47°' 
The  mechanifm  of  fecretion  appears  to  be  more 

compound,  where  that  procefs  is  performed  by 
means  of  glands,  under  which  denomination  we 
generally  include  even  follicles  and  crypto  them- 
felves ;  fuch,  for  example,  as  are  eafily  difcover- 
able  in  the  fauces  ;  and  which  phyfiologifts  gene- 
rally defignate  by  the  name  of  glandula  Jim- 
H/Jima, 


We  bellow,  with  propriety,  the  denomination 
of  fecreting  glands,  on  thofe  bodies  which,  (to 
diflinguifh  them  from  the  conglobate,  belonging  to 
the  lymphatic  fyflem),  are  called  conglomerate ;  ex- 
amples of  which  we  have  in  the  falivary  glands,  in 
the  pancreas,  in  the  lachrymal  glands,  and  in  the 
mamma,  or  breads  of  females.  The  foregoing 
glandular  bodies  are  furniflied  with  excretory 
duels,  which  are  compofed  of  tubes  or  canals 
running  imraediatelv  from  their  larger  lob^s :  thefe 

lobes, 


96  OF  SECRETION. 

lobes,  on  being  fubmitrcd  to  farther  examination, 
are  found  to  be  made  up  of  fmaller  lobules,  re- 
fpc&itig  the  internal  (lru£lure  of  which,  there  for- 
merly exiled  very  warm  controverfies  in  fome  of 
the  moil  celebrated  fchools  of  medicine.  Malpighi 
confidered  the  fmall  miliary  globules,  which  may 
be  readily  demonlrated  in  the  greater  part  of 
them,  to  be  nothing  elfe  than  genuine  acini  or 
kernels^  containing,  each  cnc,  a  minute  cavity  in 
its  centre.  While  Ruyfch  contended,  on  the 
other  hand,  that  thofe  hypothetical  excavated 
kernels  were  nothing  more  than  globular  convo- 
lutions of  extremely  fine  blood  veiTels  ;  which  lat- 
ter opinion,  is  doubtlefs  founded  on  by  far  the 
moll  unequivocal  and  fubftantial  teftimony,  as 
we  readily  learn  from  well  conduced  anatomical 
invefligations,  more  efpecially  from  fuccefsful 
injections,  and  the  aUhlance  of  glaffes. 

§  471' 
Nor  does  this  ftruclure  (if  indeed  we  keep  cut 
of  view  the  peculiar  parenchyma  of  each  parti- 
cular vifcus),  differ  much  from,  but  appears  rather 
to  fned  a  confidefable  gleam  of  light  on,  the  flruc- 
ture  of  certain  other  fecreting  vifcera,  particularly 
en  that  of  the  liver  and  kidneys,  in  which  late  ex- 
perimenters have  been  able  to  demonstrate,  with 
the  utmdft  pcrfpicuity,  certain  fpherical  bodies 
entirely  firnilar  to  the  globular  convolutions  of 
4  Ruyfch, 


OF  SECRETION.  97 

Ruyfch,  or  the  kernel-like  fubftances  of  the  cele- 
brated Malpighi.  For,  in  what  is  called  the  cortical 
portion  of  thofe  vifcera, minute  ramifications  emerg- 
ing from  the  fides  of  the  fmall  capillary  arteries,  be- 
come prefently  convoluted,  in  fuch  a  manner,  as  to 
form  little  vafcular  balls,  which  thus  appear  to  hang 
by  thofe  ramifications  of  which  they  are  compofed, 
like  fo  many  fmall  berries  or  grapes  fupported  by 
their  footflalks.  From  thefe  minute  vafcular  balls 
originate  firjit  that  very  fubtle  and  colourlefs 
order  of  veffels  immediately  deftined  for  the  bufi- 
nefs  of  fecretion,  (refpe&ing  the  origin  of  which, 
from  the  evanefcent  terminations  of  arteries,  we 
tranfiently  fpoke  on  a  former  occafion,  (§  79. 
8 1.)  j  andfecond/y,  the  incipient  radicles  of  veins, 
into  which  the  minute  arteries  are  themfelves 
continuoufly  reflected,  and  which  conduct  back 
to  the  venous  trunks,  the  refidue  of  the  blood 
now  deprived  of  thofe  elementary  particles  necef- 
fary  to  conditute  the  fluid  recently  fecreted. 

§  472- 
Finally,  certain  other  parts  of  the  body,  appro- 
priated entirely  to  the  bufinefs  of  fecretion,  are 
diftinguifhed  again  by  different  and  remarkably 
peculiar,  fpecies  of  organization  ;  thus  the  male 
teftes,  for  example,  are  wholly  compofed  of  no- 
thing elfe  than  clofe  and  mazy  convolutions  of 
very  lengthy  and  numerous  blood  vefTels,  &c. 


vol.  n.  G  §  47 


,■>* 


0  OF  SECRETION 

§  473- 
We  come  now  to  the  confideration  of  the  pe- 
culiar caufes,  by  the  operation  and  efficacy  of 
which  thofe  determinate  and  fpecifk  humours  are 
fecreted  in  thefe  correfponding  determinate  and 
fpeciflc  organs :  this  is  indeed  the  Gordian  knot — 
this  is  by  far  the  mofl  difficult  point  of  difquifition 
in  the  whole  doctrine  of  fecretion — that  point 
which  numerous  doubts  and  difficulties  yet  invert. 

§  474- 
It  appears  indeed  to  be  a  truth  afcertained  and 

eftablifhed  beyond  the  faintefl  fhadow  of  a  doubt, 
that  the  leading,  and  what  may  be  called  the 
proximate  caufe  of  mod  of  the  fecretions,  mult 
be  fought  for  in  the  internal  ftru&ure  of  the  fe- 
treting  organs  themfelves :  under  this  head  we 
mufh  particularly  confider,  in  the  conglomerate 
glands  and  other  fecreting  vifcera,  not  only  the 
peculiar  diilribution  and  direction  of  the  extreme 
blood-velTels,  from  which  the  humours  are  fe- 
creted, but  alfo  the  parenchyma^  fo  uniformly 
proper  to  each  fecreting  vifcus,  that  in  many  of 
them  it  can  be  inftantly  known  and  diftinguifhed 
at  firft  fight  from  all  other  kinds  or  fpecies  of 
fiem  (§  27). 

§  475- 
It  is  alfo  an  opinion  extremely  probable  (in 
fupport  of  which  we  have  advanced,  on  former 

occafions, 


OF  SECRETION.  9 

cccafions,  feveral  arguments  not  eafily  refuted)* 
that  the  fecreting  vifcera,  befides  their  peculiar 
parenchyma,  poffefs  alfo  what  we  have  taken  the 
lilxrry  to  call  a  vita  propria,  i.  e.  a  fpecific  or 
exclufive  kind  of  vital  energy,  effentially  different 
from  what  we  denominated  the  three  commo?i 
energies,  namely,  contractility,  irritability,  and  fen- 
Ubility. 

§  476- 
But  further,  if  my  views  of  the  fubject  be  in 
any  meafure  juft,  the  abforbent  fyjlem  appears  to 
contribute  alfo  a  very  important  part  towards  the 
promotion  of  the  feveral  fecretions :  thus,  from 
each  of  the  fecreting  vifcera  certain  appropriate 
branches  of  this  fyftem  abforb  and  re-convey  to 
the  blood-veffels  larger  or  fmaller  portions  of  each 
of  the  feveral  humours  to  which  thefe  vifcera  give 
origin  \  the  uniform  cenfequence  of  which  is* 
that  the  blood  becomes  literally  impregnated  with 
the  contagion  of  every  humour  fecreted  in  the 
different  parts  of  the  body,  e.  g.  with  bile  from 
the  liver,  Wnhfemen  from  the  telles,  &c. 

Thus  there  appears  to  exift,  in  the  fyftem  de- 
fined for  the  bufinefs  of  fecretion,  a  perpetual 
routine  or  circulation,  fo  that  the  elementary 
parts  of  the  humours  already  fecreted  being  in- 
ceffantly  conveyed  from  the  fecreting  organs 
G  2  them- 


jdo  OF  SECRETION. 

themfelves,  are  united  afrefh  to  the  mafs  of  blood, 
and  on  their  fubfrquent  return  to  their  parent 
organs,  in  conjunction  with  the  fanguineous  cur- 
rent, are  again  more  eafily  attracted  by  the  fe- 
creting  veffels,  in  confequence  of  a  peculiar  law 
of  affinity,  and  have  alfo  a  power  of  drawing 
along  with  them  thofe  parts  of  the  blood  that 
are  mod  homogeneous  in  their  nature,  and  for 
which  they  confequently  poflefs  the  higheft  de- 
cree of  attraction. 

§  477- 

To  facilitate  the  fecretion  of  certain  hianours 
of  the  body,  adequate  provifion  is  made  by  the 
production  of  fpecific  qualities,  in  thofe  particular 
portions  cf  the  blood  from  which  they  are  to  be 
proximately  derived  :  thus  the  bile  is  fecreted 
from  the  blood  of  the  vena  portarum,  a  portion 
of  fluid  highly  impregnated  with  phlogifton,  fur- 
niflied  in  profufion  by  the  abdominal  fourccs,  from 
which  this  blood  immediately  originates. 

§  478. 

I  pafs  in  filence  over  certain  other  co-operating 
aids,  which  act  in  fubfervience  to  particular  fecre- 
tions,  as  congejiion  and  derivation,  fo  evidently 
efficacious  in  the  fecretion  of  milk,  with  other  in- 
stances of  a  fimilar  nature. 


S  479- 


OF  SECRETION,  io£ 

§  479- 
Among  the  humours  thus  fecreted  by  the  or- 
gans which  we  have  juft  defcribed,  and  by  the 
powers  or  caufes  jufl:  enumerated,  it  may  be  ob- 
fcrved  that  the  following  difference  afterwards 
exifts,  namely,  while  fome  of  them  drop  imme- 
diately from  their  fecreting  organs  into  the  places 
of  their  ultimate  deftination,  in  which  they  are  to 
perform  their  fpecific  functions,  others  again  are 
conveyed  to  appropriated  receptacles,  in  which 
they  are  retained  for  fome  time,  and  thus  farther 
matured  previoufly  to  their  final  elimination  from 
the  fyftem  :  of  this  laft  defcription  is  the  milk 
which  ftagnates  in  the  lactiferous  ducts,  the  urine, 
the  bile,  and  the  femen  mafculinum,  which  are 
fubjected  to  retention  in  their  veficular  receptacles, 
and  finally,  the  ferum  contained  in  thofe  veficles 
which  were  firfl:  difcovered  by  de  GraafF  in  the 
ovaria  of  the  female. 


G  3  SECT, 


foj  OF  THE  URINE,       / 

SECT.    XXXVIII. 
OF  THE  URINE. 

JjE  SIDES  the  nutritions  juices  and  the 
fecreted  humours  deftined  for  further  fervices  in 
the  animal  economy  (§  4.),  the  blood  furniihes 
alfo  materials  for  the  formation  of  certain  ufelefs 
and  fuperfluous  liquids,  that  are  intended  to  be 
entirely  eliminated  from  the  fyftem,  and  are  from 
thence  vulgarly  called  excrements  of  ihe  fecond  di- 
gejlion.  Thtfe  excrementitious  liquids  are  of  two 
kinds,  one  of  which  is  exhaled  by  the  procefs  of 
perfpiration,  and  has  already  engaged  our  parti- 
cular attention  ;  the  other  is  the  ufine,  a  liquid 
fecreted  in  thofe  glands  denominated  kidneys. 

§  481- 
The  kidneys  are  two  vifcera  fituated  behind  the 
peritoneum,  on  each  fide  of  the  fpine,  and  in  the 
upper  part  of  the  lumbar  region  :  Although  their 
figure  is  generally  fomewhat  flatted,  yet  it  is  pro- 
per to  obferve,  that  both  in  this  refpecl,  and  alfo 
in  point  of  number,  they  are  fubject.  to  more  va- 
rieties than  any  other  vifcus  belonging  to  the  hu- 
#nan  body  :  they  hang  by  vefTels  commonly  called 

emulgents 


OF  THE  URINE.  103 

emulgents  (remarkably  large  in  proportion  to  the 
magnitude  of  the  parts  on  which  they  are  distri- 
buted), and  are  cufhioned  round  by  fat  of  a  feba- 
ceous  confidence  (§  38). 

§  4S2. 
They  are  inverted  by  a  proper  membrane,  of 
an  elegant  vafcular  ftru&ure  :  each  one  of  them, 
efpecially  during  the  period  of  infancy,  appears  to 
be  compofed  of  about  eight,  or  fomewhat  more, 
kidney-form  lobes  or  fubdivifions ;  each  of  which 
confifts  again  (according  to  an  opinion  formerly  en- 
tertained and  taught  by  Ferrein),  of  about  feventy 
or  eighty  fiefhy  radii,  which  that  phyfiologift 
called  white  pyramids. 

§  483- 
If  the  kidney  be  differed  or  divided  from  its 
convex  dorfum  towards  its  concave  pelvis,  it  ex- 
hibits in  its  compofition  two  kinds  of  fubftance ; 
one  forming  its  circumference,  and  therefore  de- 
nominated its  cortical,  the  other  conflicting  its 
centre,  and  hence  called  its  medullary,  portion. 

Each  portion  abounds  with  Sanguiferous  arte- 
ries and  veins  ;  befides  which,  the  external  cortex 
is  alfo  furniihed  with  an  additional  order  of  very 
minute  colourlefs  vefTels,  deftined  to  fccrete  the 
urine :  while  the  medulla  contains  alfo  veffds  of 
G  4  a  fimilar 


•  •4  OF  THE  URINE. 

a  fimilar  description,  intended  to  carry  it  onward 
when  fecreted. 


Thofe  fecretory  ducts  originate,  in  the  manner 
already  defcribed  (§  47 1.),  from  the  fmall  glo- 
bular convolutions  of  capillary  arteries  that  are, 
every  where  interfperfed  throughout  the  cortex 
of  the  kidney :  thofe  duels  conftitute  indeed  by 
far  the  greater  portion  of  the  cortical  fubftance 
of  the  kidney,  and  may  be  very  eafily  diftinguifhed 
by  their  fmgular  meanderings  and  intricate  mazes, 
from  the  fmall  conducting  tubes  of  Bellini,  in  which 
they  finally  terminate.  Thefe  tubuli  Belliriiani 
(as  they  are  frequently  termed)  pafs  by  a  direct 
route  from  the  cortical,  and  enter  the  medullary 
fubftance,  of  which  they  conflirute  bv  Br  the 
greater  part ;  and  uniting  afterwards  by  reiterated 
coalitions  into  a  fmall  number  of  narrow  trunks, 
finally  perforate,  by  their  extreme  orifices,  in  a 
fieve-like  manner  ,the  feveral  papilla,  contained  in 
the  renal  pelvis, 

§  484- 

The  papillx  correfpond  for  the  moft  part  to  the 
number  of  lobes,  of  which  we  already  faid  each 
kidney  is  compofed.  The  urine  that  is  fecreted 
in  the  colourlefs  veiTcls  of  the  cortex,  and  after- 
wards conduced  through  the  tubuli  Belliniani  oi 
she  medulla,  thefe  papilla?  difcharge  into  their 

£orrcfpoiid;n^ 


OF  THE  URINE.  105 

correfponding  infundibula,  which  form  by  their 
fubfequent  confluence  the  common  pelvis, 

§  485- 
The  pelvis  is  continued  into  the  ureters,  which 
are  membranous  canals,  exquifitely  fenfible,  and 
defended  internally  by  a  complete  inveftiture  or 
lining  of  mucus  j  they  are  capable  of  extreme  di- 
latation ;  in  man  they  are  here  and  there  uneven 
in  the  width  of  their  cavities,  and  are  at  length 
inferted  into  the  pofterior  furface,  not  far  from 
the  neck  of  the  urinary  bladder.  This  infertion 
is  effected  in  fuch  a  manner,  that  the  ureters  do 
not  immediately  perforate  the  parietes  of  the  uri- 
nary cyft,  but  defcend  a  fhort  diRance  between 
its  mufcular  and  nervous  coats  (which  are  here 
poffefTed  of  more  than  ordinary  thicknefs),  and 
open  finally  into  the  cavity  of  this  organ  by  ob- 
lique orifices.  By  means  of  this  ilrufture,  ade- 
quate provifion  is  made  to  prevent  the  urine,  that 
has  once  entered  the  cavity  of  the  bladder,  from 
being  forced  to  return  again  into  the  ureters  by 
an  inverted  or  retrograde  motion. 

§    486, 

In  an   adult  fubject,  the  urinary  bladder  is  in 

general  fufficiently  capacious  to  contain  about  two 

pounds  of  urine  ;   its  fundus  or  bottom,  which  in 

fetal  (late  terminates  in  the  uracbus,  and  alfo 


ic<5  OF  THE  URINE. 

its  pofterior  fide,  are  inverted  by  the  peritoneum  ; 
as  to  its  remaining  membranes  or  coats,  they  bear 
a  general  refcmblance  to  thofe  of  the  ftomach,  of 
which  we  have  already  fpoken. 

The  mufcular  coat  confifts  indeed  of  interrupted 
bands  of  flefhy  fibres,  that  furround  the  cy.t, 
forming  at  the  fame  time  various  irregular  decuf- 
fations  or  interferons,  which  are  different  in  dif- 
ferent fubje&s  :  this  mufcular  coat  phyfiologifts 
denominated  detrufor  urinte,  while  they  defignate 
by  the  name  of  fp hinder  vc/tca,  thofe  orbicular 
fibres  that  partially  furround  the  neck  of  the  blad- 
der, though  they  are  very  inconftant  and  irregu- 
lar, both  with  refpecl  to  their  figure  and  origin. 

The  nervous  coat  bellows  on  this  membranous 
vifcus  alfo  the  principal  part  of  its  flrength  and 
firmnefs. 

Finally,  the  internal  coat,  which  is  confidered 
by  phyfiologifts  as  a  procefs  or  continuation  of  the 
epidermis,  is  defended  by  a  complete  covering  of 
mucus,  efpecially  round  the  neck  of  the  bladder. 

§  4^7- 
Befides  thofe  public  and  well  known  routes  of 
the  urine,   of  which  we  have  already  fpoken,  it 
appears  probable  from  feveral  phenomena,  that 

there 


OF  THE  TJRINE.  107 

there  exifl  alfo  certain  fecret  avenues,  which  lead 
immediately  from  the  interlines  to  the  nropoietic 
organs.       For   the   fpeedy  difcharge  of  certain 
drinks  from  the  urinary  emun&ory,  fo  frequently 
imbued  with  the  odour,  tinctured  with  the  colour, 
and  characterized  by  other  fpecific  qualities  of  the 
aliments  recently  taken  in,  will  fcarcely  admit  the 
belief,  that  thefe  liquids  had  performed,  in  fo  (liort 
a  time,  the  cuftomary  long  and  circuitous  route 
through  the  thoracic  duel  and  fanguiferous  fyf- 
tem  :   to  the  foregoing  circumftance  we  may  add 
an  account  we  have  read,   of  the  urine  having 
been  found  covered  with  oil,  that  entered  into  the 
compofition  of  an  enema,  which  had  been  previ- 
oufly  and  recently  thrown  into  the  inteftinum  rec- 
tum.    It  is,  on  the  other  hand,  a  circumftance 
well  known  to  phyfiologifts  of  the  prefent  day, 
that  very  ftriking  and  numerous  anaftomofes  oc- 
cur between  the  lymphatic  veflels   of  the  intef- 
tines,  and  thofe  of  the  kidneys.     Laflly,  it  is  now 
unequivocally  afcertained  and  confirmed  by  live 
directions,  that  if  both  ureters  of  a  dog  be  tightly 
enclofed   in   ligatures,   and   his  bladder  perfectly 
evacuated  of  its  contents,  this  latter  organ  will, 
notwithstanding,  in  the  term  of  three  hours  after- 
wards, contain  a  certain  quantity  of  urine  ;  while 
•at  the  fame  ti;re  the  ufual  avenues  of  this  fluid, 
namely,  the  ureters,  are  completely  obftructed,  as 
is  evident  from  this  circumftance,  that  above  the 

ligatures 


foft  OF  THE  URINE. 

ligatures  thefe  tubes  fuffer  vaft  diftention  from  the 
accumulated  urine. 

§  488. 
But  through  whatever  avenues  the  urine  has 
been  conveyed  to  the  bladder,  its  gradual  accu- 
mulation in  that  organ  excites  an  uneafy  fenfation, 
which  becoming  urgent  and  troublefome  (§  331.) 
potently  folicits  its  final  elimination,  through  an 
emiffary  or  fewer  deftined  for  that  particular  pur- 
pofe,  namely,  the  urethra.  This  excretory  canal 
16  fubje&ed  to  a  variety  in  its  conformation,  found- 
ed on  the  diverfity  of  the  fexes,  of  which  we  will 
fpeak  more  amply  when  treating  profeffedly  of 
the  fexual  functions. 

§  4S9- 
In  order  to  evacuate  the  bladder,  it  is  neceffary 
to  overcome  the  contraction  of  its  fphin&er,  by 
the  exertion  of  its  own  detrufor  (of  which  we  for- 
merly fpoke)  (§  486.),  aided  by  the  co-operation 
of  the  abdominal  mufcles,  and  thofe  fubiervient 
to  the  procefs  of  refpiration  ;  to  which,  in  males 
of  the  human  fpecies,  we  may  add,  laftly,  the 
action  of  the  mufculi  accc!a\itores,  which  forcibly 
ejaculate,  perfaltumt  as  it  were,  even  the  refiduary 
drops  of  urine  that  may  be  occafionally  lodged  in 
the  bulb  of  the  urethra. 

S  49^ 


OF  URINE.  to? 

§   49°- 

As  to  the  nature  of  the  urine  itfelf,  it  is  fubjeft 
indeed,  to  an  infinitude  of  varieties  generated  by 
the  circumftances  of  age,  and  feafon,  but,  above 
all,  by  the  longer  or  fhorter  term  of  time,  fubfe- 
quent  to  the  previous  ufe  of  food  and  drink,  the 
difcharoje  of  this  fluid  occurs ;  to  which  may  be 
alfo  added,  the  quality  of  the  aliment  previonfly 
ufed,  Sec.  In  general,  however,  when  we  exa- 
mine the  urine  which  is  difcharged  by  a  healthy 
human  adult,  immediately  after  found  and  tran- 
quil fleep,  we  difcover  it  to  be  a  watery  liquid,  of 
a  nidorous  faiell,  and  citron  colour,  containing  in 
its  aqueous  medium,  (as  in  a  common  vehicle} 
various  elementary  fubilances,  efpecially  earthy 
and  filine,  which  bear  different  proportions  to 
each  other  in  different  individuals,  and  even  in 
the  fame  individual  at  different  times  and  under 
the  influence  of  different  circumftances.  Of  the 
terrene  elements  the  moil  abundant  is,  in  general, 
calcareous  earth,  which  is  not  unfrequently  found 
in  the  urinary  parages  under  the  form  of  calculi, 
but  which  is,  notwithstanding,  extremely  variable 
and  inconftant  in  its  quantity.  Of  all  the  falins 
matters,  that  mod  worthy  of  being  mentioned,  is 
the  effcntial  and  native  fait  of  urine — called  alfo, 
microcofmic  fait,  fuf.ble  fait ,  &c.  This  faline  fub- 
ftance  contains,  in  a  greater  proportion  than  any 

othcr 


j  ra        6F  SEXUAL  DISCRIMINATION. 

other  part  of  the  human  body,  the  celebrated 
phofphoric  acid  chemically  efpoufed  to  the  volatile 
alkali. 


SECT.     XXXIX. 

OF  THE  DISCRIMINATION  OF  THE  SEXES  IN 
GENERAL. 

§  49T- 

1  HOSE  functions  of  the  human  body, 
in  the  confideration  of  which  we  have  been  hi- 
therto engaged,  are  indeed  poflefTed,  and  exercifed 
in  common,  by  the  individuals  of  each  fex  :  with 
refpccl:  to  the  mode,  however,  in  which  fome  of 
them  are  performed,  there  occur  between  the 
two  fexes  no  inconfiderable  degrees  of  difference. 
Of  this  difference,  it  may  be  proper  briefly  to 
enumerate  the  leading  points,  previoufly  to  our 
entrance  on  the  confideration  of  what  are  denomi- 
nated the  fexual functions. 

§  492- 
To   fpeak,  then,   in  general  terms,  each  fex 

poffefTes  and  exhibits  its  own  peculiar  habit,  which 
differs  conMerably  from  that  of  the  other.     In 

the 


OF  SEXUAL  DISCRIMINATION.         n* 

the  human  fubjeft  after  birth,  this  difference  of 
habit  is  diftinttly  obfervable  ;  but  during  the. ten- 
der fcetal  (late,  is  fcarcely  to  be  diflinguifhed, 
unlefs  by  more  clofe  and  pointed  attention  j 
neither  indeed,  in  this  ftate,  can  the  external 
organs  of  generation  themfelves  be  difcriminated, 
on  a  tranfient  and  fuperficial  view,  owing  to  the 
extraordinary  magnitude  and  prominency  of  the 
female  clitoris,  and  the  very  diminutive  fize  of  the 
male  fcrotum. 

§  493- 
During  the  period  of  infancy  this  difference  of 
the  general  habit,  depending  on  the  diverfity  of 
fex,  makes  only  a  flight  impreffion  on  the  ob- 
ferver ;  but  becomes  gradually  more  and  more 
obvious  and  ffriking  till  the  full  completion  of  the 
years  of  puberty,  at  which  period,  the  general 
conformation  of  the  female  body,  its  tendernefs, 
its  foftnefs,  and  the  ufual  inferiority  of  its  ffature, 
contrafted  with  the  athletic  and  robuft  body  of 
die  male,  exhibit  this  general  habitual  difference 
in  the  mod  ftriking  point  of  view. 

§  494- 
Similar  to  the  difference  that  occurs  between 

the  external  habits  of  body,  that  chara&erife  the 
two  fexes,  is  that  which  is  obfervable  in  the  bones 

them- 


ri2         OF  SEXUAL  DISCRIMINATION*. 

thcmfelves.  Thefe  folid  portions  (all  other  cir- 
cumftances  being  alike)  are  evidently  much  more 
fmooth  and  round  in  females  than  in  males ;  the 
cylindrical  bones,  in  particular,  are  more  flender 
and  delicate,  and  the  plane  ones  more  attenuated 
or  thin,  in  the  former,  than  in  the  latter  fex ;  not 
to  mention  the  peculiar  diverfities  of  certain  re- 
markable bones,  particularly  thofe  of  the  thorax 
and  pelvis,  with  the  clavicles,  the  femora,  &c. 

§   495- 
With  refpec"r.  to  the  foft  parts  of  the  body,  we 

may  obferve  in  general,  that  in  females,  the  cel- 
lular membrane  is  more  lax,  more  pliable,  and 
confequently  more  readily  dilatable  in  the  ftate  of 
pregnancy :  while  the  fkin  is  more  tender,  fair 
and  beautiful,  in  confequence  of  the  immediate 
fubftratum  of  fat. 

The  hair  of  the  head  is  generally  of  a  greater 
length  in  females  than  in  males  ^  while  at  the  fame 
time,  certain  other  parts  of  the  body  which  in  the 
latter  are  rough  and  hairy,  are  in  the  former' 
either  perfectly  fmooth,  as  the  chin  and  bread ; 
lefs  hairy,  as  the  perineum  ;  or  planted  with  only 
a  very  tender  and  foft  down,  as  the  arms  and 
legs, 

x  %  496. 


OF  SEXUAL  DISCRIMINATION.         113 

§   496- 

When  fpeaking  of  the  diverfities  of  particular 
functions,  we  mull  not  filently  pretermit  the  pulfe, 
which  (other  circumftances  being  alike)  is  more 
frequent  in  females  than  in  males,  (§  109).  In 
the  former,  the  thorax  is  Subjected  to  a  greater 
degree  of  motion,  (especially  at  its  fuperior  part,) 
than  in  the  latter  ;  the  os  hyoides  is  much  fmaller, 
the  larynx  is  lefs  capacious,  and  hence  the  voice 
more  drill. 

S  497- 

With  regard  to  the  animal  functions,  it  is  ne- 
ceflary  to  obferve  in  general,  that  in  females  the 
mobility  of  the  nervous  fyftem  is  much  greater 
than  in  males,  the  irritability  is  more  exquiiite ; 
and  the  propenfity  to  commotions  of  the  mind, 
more  prompt  and  Spontaneous. 

§  498- 

As  to  the  natural  functions,  the  appetite  for 
food  is  weaker  in  the  female,  than  in  the  male 
fex  ;  while,  en  the  other  hand,  the  increafe  of  the 
body  is  more  rapid  in  the  former,  and  the  (late  of 
puberty  and  mature  growth  attained  at  an  earlier 
period. 

vol.  II.  H  §   409. 


n4         OF  THE  GENITAL  FUNCTION 

§  499- 
But  by  far  the   greateit   and   mod   important 

cHfJinftion  of  the  fexes  is  derived  from  the  genital 
functions  themfelves,  the  male  being  furnimed 
with  a  power  of  fecundation,  and  the  female  with 
that  of  conccbtimi.  A  farther  inveftiijation  of  thefe 
powers  (hall  engage  the  greater  part  of  our  atten- 
tion, throughout  the  remaining  pages  of  this 
work. 


SECT.     XL. 
OF  THE  GENITAL  FUNCTION  OF  THE  MALE  SEX. 


§    500' 


-a.  HE  genital  liquor  of  the  male  is 
prepared  by  the  tefles,  two  bodies  fufpended  in 
the  fcrotum  by  their  fpermatic  cords,  and  (befides 
the  lymphatic  veins  with  which  they  abound  in 
profufion),  compofed  chiefly  of  three  kinds  of 
veffels. 

Thefe  are  firji,  the  fpermatic  artery,  which  in 
proportion  to  its  {lender  diameter  is  faid  to  be  the 
longeft  of  all  the  arteries  belonging  to  the  human 

body ; 


OF  THE  MALE  SEX.  115 

body  :  it  in  general  conveys  the  blood  immedi- 
ately from  the  abdominal  portion  of  the  uona 
itfelf,  to  the  body  of  the  teflis. 

Secondly,  the  duel  us  deferens,  which  carries  to 
the  vificula  feminales,  the  femen  when  once  fe- 
crcted  from  the  arterial  blood. 

And,  laftly,  what  is  commonly  denominated  the 
pampiniform  plexus  of  veins,  the  function  of  which 
is  to  receive  and  convey  to  the  cava  or  emulgent 
vein,  the  blood  that  remains  after  the  procefs  of 
fecretion  is  accomplifned. 

§  501. 
The  teftes  are  not,  from  the  time  of  their 
earlieft  forms tion,  fufpended  in  the  fcrotum,  as 
reprefented  in  the  above  defcription  :  thus  in  the 
male  fectus,  while  yet  in  a  very  tender  and  imma- 
ture ftate,  thofe  gtandular  bodies  occupy  indeed 
a  very  different  fituation,  the  reafon  and  fuccelllve 
changes  of  which  were  firQ:  accurately  inveftigated 
and  detailed  by  Hal!er,  at  Gottengen  in  the  year 
1749,  but  were  afterwards  explained  by  other 
writers  on  principles  fo  different  from  each  other, 
as  to  have  given  rife  to  various  controvcrfies  of 
fomc  weight  and  importance.  Of  the  fituation 
and  changes  of  the  teftes  in  the  fecial  ftate,  I  am 
prepared  to  lay  before  the  reader  a  brief,  though 
H  2  compre- 


n6         OF  THE  GENITAL  FUNCTION 

comprehenfive  account, — the  fpontaneous  refult 
of  numerous  obfervations  made  on  nature  herfelf, 
during  a  remarkable  feries  of  difleclions  of  male 
embryo's,  in  which  1  engaged  for  the  exprefs 
purpofe  of  (liedding  light  on  this  fubject  fo  inte- 
resting to  phyfiologifts. 

§  502- 
On  opening  the  lower  abdominal  region  of  an 
immature  foetus,  we  difcover  in  each  groin,  near 
what  is  called  the  ring  of  the  oblique  mufcles,  a 
very  narrow  orifice  in  the  membrane  denominated 
peritoneum  ;  this  orifice  is  the  threshold  to  a  (trait 
avenue  or  alley,  as  it  were,  that  leads  through  the 
abdominal  ring  itfelf,  and  terminates  afterwards 
in  a  peculiar  bullous  or  bubble  like  fack  :  this 
fack  extends  without  the  abdominal  cavity,  looks 
towards  the  fcrotum,  is  interwoven  with  cellular 
fibres,  and  deftined  for  the  future  reception  of 
the  teftis. 

§  5°3> 
At  the  very  pofterior  margin  of  this  fmall 
abdominal  orifice,  the  peritoneum  fends  off  an- 
other procefs,  which  mounts  upwards,  and  in  the 
tender  foetus  reprcfents,  in  the  greater  part  of  its 
courfe,  a  longitudinal  fold  :  from  the  bails  of  this 
procefs  a  (lender  cylinder,  or  rather  inverted  cone 
afcends,  and  forms  at  its  fummit,  which  regards 

the 


OF  THE  MALE  SEX.  117 

the  inferior  margin  of  the  kidney,  a  fmall  blifter 
or  fack-Iike  termination  ;  in  this  fack  the  teflis 
and  epididymis  are  enclofed  ;  fo  as  to  refemble, 
at  firft  fight,  a  fmall  berry  reding  on  its  footflalk, 
and  appear,  at  the  fame  time,  to  hang  loofeiy  into 
the  abdominal  cavity  fomewhat  like  the  liver  or 
fpleen  (§   404). 

§  5°4- 
The  veffels  which  are  afterwards  to  conftitute 
the  fpermatic  cord,  are,  at  this  very  early  period, 
feen  running  behind  the  extremely  tender  and 
pellucid  peritoneum,  (o  that  the  fpermatic  artery 
and  vein  run  in  a  defcending  dire&ion  along  the 
fides  of  the  fpine,  while  the  vas  deferens  bending 
fomewhat  inwardly  towards  the  neck  of  the  uri- 
nary bladder,  ftretches  along  the  loofe  cellular 
membrane,  which  is  fituated  behind  the  perito- 
neum, and  both  enter  the  body  of  the  teftis  in 
that  peritoneal  plica  or  fold  of  which  we  have 
already  fpoken. 

§  5^5- 
From  about  the  middle  liage  of  pregnancy,  the 
teftes  begin  to  fink  downward  by  degrees,  fo  as 
gradually  to  approach  the  narrow  orifice  of  the 
peritoneum,  which  has  been  already  mentioned. 
At  the  fame  time,  the  foregoing  peritoneal  fold, 
with  its  cylindrical  attachment,  are  wrapped  up 
H  3  by 


ii3         OF  THE  GENITAL  FUNCTION 

by  decrees,  till  the  teflis  finally  refrs  on  the  very- 
mouth  of  the  preceding  canal. 

§  506, 
When  in  the  fcetus,  now  advanced  to  a  higher 
flage  of  maturity,  the  teflis  is  fully  prepared  for 
a  final  defcent,  the  orifice,  hitherto  fo  contracted 
cr  narrow,  fuffers  fuch  a  remarkable  dilatation, 
that  the  teftis  is  at  full  liberty  to  enter  with  facility 
the  opening  that  leads  out  of  the  abdomen  as  well 
as  the  ring  by  which  this  opening  is  furrounced, 
to  pafs  onward  through  the  whole  length  of  the 
canal,  and  thus  plunge  headlong,  as  it  were,  into 
the  bliiler-like  fac  of  which  we  have  already  fpo- 
ktn.  The  teftis  having  finally  accomplished  its 
defcent,  the  peritoneal  opening  is  foon  after  clofed 
in  the  molt:  complete  manner,  and  even  fubjected 
in  a  fhort  time  to  a  perfect,  adheilon  of  its  fides,  (o 
that  in  the  flage  of  infancy,  fcarcely  a  wreck  of 
it  is  left,  to  point  the  enquirer  to  the  place  of  its 
former  exigence. 

§  S07- 
The  more  gradual  and  flow  the  movement  of 
the  teflis  (while  yet  in  the  abdominal  cavity)  to- 
wards the  orifice  of  its  egreflion,  the  more  fud- 
den  and  inftantaneous  appears  to  be  its  act  of 
tranfition  through  the  abdominal  ring.  For  in 
the  difTeclions  of  mature  fcetufes,  it  is  by  no  means 

uncom- 


OF  THE  MALE  SEX.  119 

uncommon  to  difcover  the  tedis  either  as  yet  in- 
cumbent on  the  peritoneal  opening,  or  elfe  ftatio- 
nary  in  the  groin,  after  having  recently  paffed  the 
abdominal  ring :  but  once  only  was  1  fo  fortunate 
as  to  have  an  opportunity  of  obferving  the  right 
tedicle  of  a  twin-fcetus  (of  which  a  complete 
drawing  has  been  given),  at  the  very  moment  ot 
its  pafTage  through  the  abdominal  ring  :  the  gland 
appeared  to  have  been  very  tightly  embraced  and 
drangled,  as  it  were,  by  the  furrounding  parts, 
and  was  apparently  in  complete  readinefs  to 
emerge  from  the  abdomen  into  its  deflined  lack ; 
a  tranfition  already  accomplished  by  the  left  tef- 
ticle,  that  had  juft  efcaped  from  the  ring,  the  ori- 
fice of  which  had  again  refumed  its  former  imper- 
vious (late. 

§  5°S- 
This  remarkable  defcent  of  the  tedes  along  the 
groins,  does  not  appear  to  be  exclufively  confined 
to  any  particular  period  of  time  :  it  occurs  for 
the  mod  part,  however,  about  the  lad  month  of 
pregnancy  :  although  thefe  glandular  bodies  are 
not  unfrcquently  found  either  in  the  abdominal 
cavity  itfelf,  or  in  the  fuperior  part  of  their  in- 
guinal route,  even  in  infants  after  birth.  For  the 
teflicle,  after  its  entire  efcape  from  the  abdomen, 
has  dill  a  further  ftage  of  its  journey  to  perform, 
namely,  its  final  defcent  along  the  groin  into  the 
II  4  fcrotum, 


i2o  OF  THE  GENITAL  FUNCTION 

fcrotum,  in  company  with  the  fmall  fa'c  by  which 
it  is  enveloped. 

§    509. 

That  the  foregoing  is  indeed  a  true  account  of' 
the  progreiTive  movement  of  the  teftcs  in  their 
defcent  from  the  abdomen  into  the  fcrotum,  I 
have  had  fufficient  opportunities  of  ascertaining 
from  repeated  observation.  To  develope  the 
caufes  and  energies  by  which  this  aftonifhing  de- 
fcent is  accomplished,  appears  to  be  indeed  attend- 
ed with  difficulties  of  the  utmoft  magnitude*  For  I 
am  daily  more  and  more  convinced,  that  neither  of 
thofe  powers  to  which  this  defcent  has  been  hither- 
to afcribed  (fuch,  for  example,  a^  the  action  of  the 
cremafter  mufcle,  the  action  of  the  diaphragm,  or 
the  contractility  alone  of  that  cellular  and  tendi- 
nous intertexturc,  which  adheres  to  the  proceiles 
of  the  peritoneum,  and  is  ufually  denominated 
gubernaculum  Hunterii,  &c),  is  fufficient  to  ex- 
plain a  movement  of  fuch  extreme  Angularity, 
efpecialiy  that  part  of  it  relating  to  the  immediate 
tranfition  of  the  teflis  through  the  narrow  abdo- 
minal ring,  to  which  the  reader's  attention  has 
been  fo  frequently  folicited  :  while  I  am  imprefled, 
on  the  other  hand,  by  a  thorough  conviction, 
that  this  whole  procefs  exhibits  the  moft  unequi- 
vocal aud  ftriking  example  of  what  we  have  de- 
nominated fpecific  life,  without  the  peculiar  opera- 
tion 


OF  THE  MALE  SEX.  121 

lion  and  aid  of  which,  it  is  fcarcely  poflible  to 
folve  the  feveral  phenomena  of  a  tranfition  fo  ex- 
tremely fingular  in  its  nature,  and  fo  widely  diffi- 
miiar  to  all  other  movements  and  functions  that 
occur  in  the  whole  animal  economy. 

The  involucra  by  which  the  tefles  are  invefted, 
after  their  final  completion  of  the  foregoing  route, 
may  be  aptly  enough  divided  into  common  and 
proper. 

The  only  involucrum  common  to  both  thefe 
glandular  bodies  is  the  fcrotum.  This  is  a  fac, 
confiiling  of  a  tender  portion  of  cutis  expanded 
over  a  thin  fubilratum  of  fat,  and  pofTefTing  a  pe- 
culiarity that  does  not  refide  in  any  other  part  of 
the  common  integuments  of  the  body,  namely,  a 
power  of  changing,  in  a  very  remarkable  degree, 
its  ufual  habit  and  appearance  :  thus,  it  fometimes 
depends  loofe  and  flaccid,  and  again  (efpecially 
under  the  impreffion  of  the  venereal  ceflrum,  or 
in  cafe  of  expofure  to  cold),  becomes  conftricled 
and  rigid,  as  it  were,  and  is  then  particularly 
marked  by  furrows  and  divernfied  rugofities. 

§    511- 
Of  thofe  involucra  which  are  proper  to  each 

teftis,  that  placed  immediately  beneath  and  within 

the 


122         OF  THE  GENITAL  FUNCTION 

the  fcrotum,  is  called  the  tunica  dartos  :  this  coat 
poffefTes  a  very  peculiar  and  vivid  contractility,  by 
which  Window,  Haller,  and  other  celebrated  cha- 
racters have  been  fo  far  deceived,  as  to  beftow  on 
it  the  nature  and  energy  of  a  mufcle. 

§  512- 
This  is  fucceeded  (after  a  voluminous  and  foft 
flratum  of  cellular  membrane),  by  three  feparate 
•vaginal  coverings,  which  were  firffc  accurately 
traced  and  diftinguiihed  by  the  ingenious  and  in- 
defatigable Neubauer. 

Of  thefe  vaginal  coats,  the  exterior  is  common 
to  the  teilicle  and  fpermatic  cord,  and  has  the  cre- 
mafter  mufcle  attached  to  it  by  feparate  bundled 
of  fibres. 

But  the  two  interior  are  proper,  one  to  the  fper- 
matic cord,  and  the  other  to  the  teftis  itfelf ;  of 
thefe  the  latter  adheres,  for  the  moli  part,by  its 
fundus  to  the  common  tunic,  while  its  internal 
furface  is  moiftcned  by  a  lubricant  fluid,  fome- 
what  after  the  manner  of  the  pericardium. 

§  5J3- 
The  origin  of  thofe  vagina]  tunics  which  has 
given  rife  to  fuch  a  variety  of  controverfies  among 
phyfiologifts,  can,  (if  I  be  not  greatly  deceived), 

be 


OF  THE  MALE  SEX.  123 

be  without  difficulty  afcertained,  from  what  has 
been  already  faid,  when  treating  of  the  defcent  of 

the  teftes. 

Thus,  the  tunica  communis,  for  example,  origi- 
nates from  the  defcending  (§  502.)  blifter-likc 
fac  or  procefs  of  the  peritoneum. 

The  propria  tejiis,  from  that  production  of  the 
peritoneum,  which  mounting  upward  in  the  form 
of  a  cylinder  (§  503.),  invcfts  the  teftis  itfclf  from 
its  earlieft  formation. 

And,  finally,  the  propria  funiculi,  from  that 
fold  of  the  peritoneum,  of  which  we  have  already 
fpoken,  and  the  {hort  cylinder  in  which  it  termi- 
nates previoufly  to  its  embracing  the  teftis  itfelf. 

§  5*4- 
Immediately  to  the  teftis  itfelf  the  tunica  albu- 
«inea  is  very  clofcly  attached,  fomewhat  after  the 
manner  of  a  cortical  covering.  From  this  tunic, 
blood-vefTels  pafs  into  the  pulp  or  body  of  the 
tefticle,  which  confifts  indeed  entirely  of  innume- 
rable vcffels,  about  a  fpan  in  length,  wound  up 
into  fmall  conglomerate  lobules  :  thefe  vefTels,  of 
which  the  fubftance  of  the  tefticle  is  compofed, 
are  both  fanguifefous  and  fecretinc-.  the  latter  of 

which 


i  24         OF  THE  GENITAL  FUNCTION 

which  conduct  the  femen,  when  prepared,  through 
the  vafcular  net-work  of  Haller,  and  the  vafa 
defferentia  of  Graaf,  into  the  beginnings  of  thofe 
cones  that  form  the  epididymis. 

§   5lS- 
That  body  which  ranges  along  the  fide  of  the 

teflis,  namely,  the  epididymis,  confifts  indeed  of  a 
fingle  veffel,  about  thirty  feet  in  length,  which  at 
one  end  (that  for  inftance  denominated  its  head), 
is  diftinguiihed  into  about  twenty  fmall  rolls  or 
cones,  and  at  its  other  (inferior)  extremity,  called 
therefore  its  tail,  increafes  gradually  in  thicknefs, 
and  thus  forms  by  its  continuation  the  vas  de- 
ferens. 

§  5>6. 

The  two  vafa  deferentia  afcending  towards  the 
neck  of  the  urinary  bladder,  and  forming  a  junc- 
tion beneath,  or  near  to,  the  proftate  gland,  are 
from  hence  bent  backward,  and  expanded  into 
the  vefizula  feminales  ;  in  fuch  a  mariner,  how- 
ever, that  thefe  veficulse,  and  the  vafa  deferentia 
themfelves,  open  by  two  common  orifices  into  the 
urethra,  jufl  behind  the  caput  gallinaginis. 

<  §  5*7- 
Finally,  the  veficula  fcminales  themfelves,  are 

attached  to  the  pofterior  furface  of  the  urinary 

cyft, 


OF  THE  MALE  SEX.  125 

cyft,  near  to  the  inferior  extremity,  or  neck,  of 
that  organ  :  they  are  imbedded  in  a  profufe  quan- 
tity of  fat,  and  from  their  diverfified  flexuofities 
and  numerous  blind  appendicula  that  moot  oft 
fomewhat  in  the  form  of  ramifications,  refemble, 
in  their  general  appearance,  two  fmall  inteftines. 

Thefe  veficula?  confifl  of  two  coats,  almoft  of 
the  fame  kind  with  thofe  that  enter,  as  formerly 
mentioned,  into  the  ccmpofuion  of  the  gall  blad- 
der ;  thus,  the  firft  or  external  coat  is  more  ro- 
bufl:,  and  fimilar  in  its  nature  to  fuch  as  are  com- 
monly denominated  nervous  ;  while  the  fecond  or 
internal  abounds  with  minute  cells  and  pits,  and 
is  every  where  divided,  by  means  of  proje&ing 
eminences,  into  minute  purfe-like  cavities,  per- 
fectly fimilar  to  thofe  that  are  fo  confpicuous 
about  the  neck  of  the  gall-bladder. 

§  5i8. 

In  thofe  organs  and  vefTels  hitherto  enume- 
rated and  defcribed,  there  is,  even  from  the  ear- 
lieit  years  of  puberty,  a  certain  fluid  fecreted 
ilowly,  and  retained  in  fmall  quantity,  namely, 
l\\efe?nen  mafculinum ;  a  liquor  extremely  fingular 
in  its  nature,  and  of  the  utmoft  dignity  and  im- 
portance in  the  animal  economy :  it  exhibits  to 
the  eye  a  milky  colour,  emits  an  odour  entirely 
peculiar,  pofTefles  a  mucoid  vifcofity,  and  is  of 

fuch 


n6         OF  THE  GENITAL  FUNCTION 

fuch  remarkable  fpecific  gravity,  as  to  furpafs,  in 
this  refpeft,  all  other  fecrcted  humours  belonging 
to  the  animal  body. 

§  5*9- 

A  peculiarity  of  this  fluid,  which  mud  not  be 
paffed  over  in  filenee,  is,  (as  was  fir  A:  obferved  by 
Lud.  Ham  at  Dantzic,  in  the  year  1677),  tnat  ic 
is  peopled  by  a  countlefs  multitude  of  microfcopic 
animalcule,   belonging  to  the  fame  order  with 
thofe   called   i??fufvria,    and    pofiefling    different 
figures,  as  they  appear  in  the  feminal  fluids  of  dif- 
ferent animals.      In  man  (and  alfo  in  the  male 
afs)  the  feminal  animalcules  exhibit  oval  figures, 
furnilhed  with  tails  of  extreme  minutenefs :  thefe 
animalcules  are  faidnot  to  be  found  in  any,  fave 
found  and  prolific  femen,  fo  that  they  appear  to 
conflitute  a  certain  adventitious  criterion  of  the 
fertilizing  maturity  of  this  important  fluid  :   we 
have  called  the  criterion  derived  from  thefe  ani- 
malcules adventitious ,  and  prefume  it  is  fcarcely 
neceffary,  at  this  enlightened  period,  to  repeat, 
that  they  iliould  not  be  accounted  the  refervoirs 
of  the  fecundating  principle,  much  lefs  fhould  they 
be  coniidered  as  the  germs  of  future  bomunculi, 
fince  fo  many,  and  fuch  weighty  arguments  and 
obfervations   have  been  lately   advanced  in  fup- 
port  of  a  different  do&rinc. 

§   520- 


OF  THE  MALE  SEX.  127 

This  genital  liquid  being  gradually  collected  in 
the  veficulse,  which  we  have  already  defcribed,  is 
there  retained  till  a  future  act.  of  excretion.  By 
fuch  retention  it  fuffers  changes  very  nearly  re- 
fembling  thofe  to  which  the  bile  is  fubje&ed  in 
confequence  of  a  flate  of  ftagnancy  in  its  cyftic 
refervoir ;  thus,  being  gradually  robbed  of  its 
aqueous  portion,  it  is  more  and  more  infpiflated 
and  approximated,  as  it  were,  towards  a  ftate  of 
concentration. 

§  521. 

For  as  the  tgfles  generally,  together  with  the 
cords  by  which  they  are  fufpended,  abound  with 
an  aftoniihing  aflemblage  of  lymphatic  vefTels, 
which  ferve  to  re-convey  from  thence  to  the 
blood  a  portion  of  fluid,  impregnated  with  the 
fpermatic  contagion,  and  by  this  means  aid  and 
facilitate  the  further  fecretion  of  femen,  on  the 
principle,  and  in  the  manner  formerly  laid  down 
(§  476.),  fo  are  the  veficula  feminaks  themfelves 
alfo  provided  with  veffels  of  the  fame  kind,  which 
by  abforbing  the  fubtle,  though  inert  water,  ren- 
der the  refidue  of  the  feminal  fluid  more  active 
and  efficacious. 

§  522- 


ii8  OF  THE  GENITAL  FUNCTION 

§  522- 
On  this  fubjett  I  doubt  much  whether  or  not, 

in  a  healthy  man,  any  genuine  femen  be  ever  ab- 
forbed  from  the  veficuls?  feminales  : — more  dill, 
whether  or  not,  as  is  fometimes  alleged,  femen 
thus  abforbed  could  be  carried  immediately  into 
the  neighbouring  fanguiferous  veins  : — but  mod 
of  all,  whether  or  not  fuch  a  feminal  abforption 
(admitting  its  real  exigence)  could  poilibly  aft  as 
an  antidote  againd  exceflive  venereal  propenfities, 
fince  it  appears  evidently,  on  the  other  hand,  that 
this  fame  abforption  would  neceffarily  operate  as 
an  exciting  caufe  of  unbridled  and  almod  infuriate 
luft :  in  quell  of  tefrimony  to  eftablifli  the  truth  of 
this  latter  proportion,  we  need  only  attend  to  the 
phenomena  of  fuch  animals  as  experience  the  ve- 
nereal propenfity  only  at  dated  feafons  of  the 
year,  and  compare  them  with  the  conditution  of 
thofe  that  have  been  reduced  to  the  date  of  cas- 
tration. 

§  5*3' 
To  me  indeed  it  appe.irs  probable,  that,  for  the 
purpofe  of  moderating  libidinous  defires,  man  is 
endowed  with  a  far  different  prerogative  (not 
conferred  on  any  other  fpecies  of  animals  with 
which  we  are  hitherto  acquainted),  namely,  that 
of  nzfiurnal  pollutions  :  thefe  evacuations  I  there- 
fore confider  among  the  natural  excretions  of  man 
i  — e vacua- 


OF  THE  MALE  SEX.  129 

' — evacuations  by  which  (as  they  occur  at  longer 
or  fhorter  intervals,  according  to  the  varieties  of 
temperament  and  conftitution),  he  is  relieved  from 
a  troublefome  and  orhenvife  urgent  impreflion 
produced  by  an  abundant  accumulation  of  femen. 

§  5H- 

It  miift  be  obferved,  however,  that  the  femen 
mafculinum  is  never  excreted  in  a  ftate  of  entire 
purity,  but  is  always  blended  with  more  or  lefs  of 
what  is  ufually  denominated  liquor  projlaia  (i.  e. 
the  liquor  of  the  proftate").  With  regard  to  the 
external  habit  and  appearance  of  this  laft  men- 
tioned liquid,  it  bears  a  very  ftriking  fimilitude  to 
the  albumen  or  white  of  eggs.  This  peculiar 
liquor  derives  its  name  from  its  immediate  birth- 
place or  fource,  which  is  a  body  of  confiderable 
magnitude,  and  of  a  fingular  and  very  compact 
parenchymatous  texture,  fituated  between  the  ve- 
fuula  fcminalcs  and  the  bulb  of  the  urethra,  and 
is  ufually  defignated  by  the  name  of  glandula  pro- 
f.aia.  The  excretory  avenues  of  this  liquor  have 
not  yet  been  fatisfaclorily  inveftigatcd  and  afcer- 
tained,  unlefs  (as  appears  probable)  they  commu- 
nicate with  the  duel:  of  the  caruncula  feminalis, 
the  orifice  of  which  opens  into  the  urethra  be- 
tween the  two  mouths  of  the  avenues  leading 
from  thofe  minute  veficles  deftined  for  the  recep- 

vol.  11.  I  tion 


i~o  OF  THE  GENITAL  FUNCTION 

tion   and  temporary  retention   of   the  fertilizing 
fenen,  (§  516). 

525. 
The  urethra  in  man  is  dellined  as  a  common 
conduit  or  emiffary  duct,  to  three  different  kinds 
of  fluids,  namely,   the  urine,  the  femen,  and  the 
liquor  of  the  proftate  gland.     It  is  lined  internally 
with  a  mucus  which  originates  from  an  immenfe 
number  of  finufes,  that  are  every  where  difperfed 
throughout  its  canal.     It  is  furrounded  by  a  fub- 
ftance  of  a  fpongy  texture,  to  which  are  fubjoined 
two  other  bodies,  fimilar  in  ftrutlure  but  far  fnpe- 
rior  in  fize,   (called  corpora  caverno/a),  that  con- 
ftitute  the  principal   part  of  the  male  penis ;  an 
organ  which  is  terminated  anteriorly  by  the  glans, 
and  wholly  invefted  by  a  very  tender  and  pliable 
portion  of  ikin  entirely  deilkute  of  all  appearance 
of  fat.     This  Ikin  forms  the  prepuce  by  its  at- 
tachment round  the  corona^  or  circular  bafe  of  the 
glans,  and  plays  over  this  body  with  a  free  motion, 
fomewhat  like  the  palpebrce  over  the  ball  of  the 
eye.     The  interior  duplicative  of  the  prepuce, 
having  affumed  a  different  appearance,  is  reflected 
over  the  glans  itfelf,  (fomewhat  like  the  adnata 
over  the  eye)  and  is  furniihed  around  the  corona, 
with  an  immenfe  number  of  the  finall  glands  of 
Liitrius,  (analogous  to  the  Meibomian  glands  of 

the 


OF  THE  MALE  SEX.  13  i 

the  palpebrce)  that  give  birth  to  a  matter  of  an 
un&uous  but  very  lingular  nature. 

§  526- 
The  male  penis,  thus  organifed  and  conftructed 
agreeably  to  the  preceding  defcription,  pofTefifes  a 
faculty  of  ere&ion,  /.  c.  in  confequence  of  an 
encreafed  conge/lion  and  impetuous  effufion  (for 
congeftion  alone  will  not  explain  the  phenomenon) 
of  blood  into  the  corpora  cavernofa,  the  penis 
fwells,  becomes  rigid,  and  changes  its  former 
pofition,  but  fuffers  again  a  deturrefcence  and 
collapfe  by  a  reabforption  of  the  fuperfluous  por- 
tion of  this  diftending  fluid. 

§  5*7' 
When  the  penis  rcfumes  its  flaccid  condition, 
it  fuffers  a  Angularly  circuitous  flexion,  at  the 
place  where  it  originates  from  the  neck  of  the 
bladder.  In  this  Mate  it  is,  indeed,  extremely 
well  calculated  for  the  excretion  of  real  urine,  but 
quite  unqualified  for  the  emiffion  of  femen,  as  the 
beginning  of  the  urethra  forms  now  a  more  acute 
an^le  with  the  fmall  orifices  of  tie  veficulse  femi- 
nales. 

§  5*8- 
When  a  gradual  intumefcence  of  the  penis  com- 
mences, there  occurs  firft  an  effufion  of  the  liquor 
I  2  furn  ifhed 


!  ;2      OF  THE  GENITAL  l7 UNCTION,   &c. 

furnifhed  by  the  proflate  gland,  which  is  often- 
times eliminated  unmixed,  but  fcarely  ever  along 
with  the  urine.  Of  this  liquor  the  primary  defti- 
nation  is,  to  be  ejected,  in  conjunction  with  the 
fcmlnal  fluid  itfelf ;  either,  that  it  may,  by  its 
albuminoid  lubricity,  qualify  the  fluggifli  tenacity 
of  the  latter  fluid,  and  thus  facilitate  and  promote 
its  ejection  ;  or  that  it  may  itfelf  contribute,  in  a 
certain  degree,  towards  the  procefs  of  generation. 

§  5*9- 
The  emiffion  itfelf  of  the  male  femen  is  excited 

as  well  by  the  immediate  impreffion  aiifmg  from 
an  abundant  accumulation  of  this  fluid  in  its  ap- 
propriated receptacles,  as  by  the  genuine  fexual 
injiincl ;  it  is  accomplifljed,  firft,  by  a  very  flrong 
ereclion  of  the  penis,  which,  while  it  obftructs  the 
paflage  of  the  urine,  paves  as  it  were,  on  the 
other  hand,  a  more  direct  and  ready  way  for  the 
tranfition  of  the  femen  ;  to  which  we  may  fubjoin, 
as  co-operating  caufes,  a  certain  fpafmodic  con- 
traclion  of  the  veficulce  feminales,  a  convulflvc 
action  of  the  levator  ani,  and  accelcratorcs  tiring, 
and  finally,  a  general  fuccujfion,  of  the  whole  ner- 
vous fyflcm,  gentle  indeed  in  degree,  and  tranfient 
in  exiftence,  but  yet  of  an  epileptic  nature,  and 
confiderably  deprefling,  in  its  effects,  on  the  ener- 
gies of  the  fyftem. 

SECT. 


OF  THE  GENITAL  FUNCTION,  fc?V.      133 


SECT.    XLI. 

OF  THE  GENITAL  FUNCTION  OF  THE  FEMALE  SEX 
IN  GENERAL. 

§    53°' 

l\.S  the  male  organs  of  generation  are 
naturally  calculated  to  give,  f )  are  the  female  to 
receive,  and  in  the  two  fexes  thefe  organs  are,  in 
a  general  point  of  view,  widely  different  from 
each  other.  It  mud  be  ohferved,  however,  that 
in  the  general  flruclure  of  certain  parts,  thefe  two 
kinds  of  organs  exhibit  no  fraall  degree  of  reci- 
procal fimilitude.  Thus  beneath  the  pubes  (the 
llruclure  of  which  has  been  already  a  fubject  of 
tranfient  attention  (§  36.)  the  clitoris  which  lies 
concealed  in  the  fuperior  commiflure  of  the  labia., 
refembles  the  male  penis  in  more  refpe&s  thau 
one,  but  is  not  furnilhed  with  a  urethra,  is  there- 
fore imperforate,  and,  (when  not  of  a  preter- 
natural proportion,)  is  remarkably  fmall.  It  is 
faid,  however,  that  this  organ  preferves,  occafion- 
ally,  even  in  adults,  the  fame  proportional  Cze, 
which,  as  formerly  obferved,  is  fo  extremely 
confpicuous  in  the  clitoris  of  the  female  embryo, 
($  492.)  Hence  appears,  in  all  probability,  to 
have  originated  mod  of  thofe  obfeene  and  fabulous 
I  3  dories, 


i34  OF  THE  GENITAL  FUNCTION 

ftoricSj  refpetting  the  exigence  of  hermaphrodites. 
This  organ  confifls  alfo,  like  the  male  penis,  o? 
corpora  cavernofa,  like  it,  is  capable  of  erection, 
like  it,  is  invefled  by  a  prepuce,  and  furnifhes, 
finally,  an  unctuous  matter  not  diffimilar  to  that 
ofLittrius,  (§  525). 

§   SV- 
From  the  clitoris  defcend  the  nymph  a,  acquiring, 

alfo,  occafionally,  an  enormous  and  preternatural 
magnitude,  (which  excefs  has,  in  like  manner,  not 
unfrequently  given  rife  to  extraordinary  and  fabu- 
lous reports)  :  they  poflefs,  in  common  with  the 
clitoris  the  mod  exquifite  degree  of  fenfibility; 
and  appear  to  give  direction  to  the  ftream  of  urine 
when  discharged,  as  the  orifice  of  the  urethra, 
(a  tube  extremely  inert  in  the  fema'e  fex,  and,  in 
the  moil  highly  fmimed  and  perfect  examples, 
ciliated  or  fiinged  in  a  very  Angular  manner),  lies 
hid,  as  it  were,  in  a  fojfla  formed  by  their  two 
bafes, 

§  S32- 
Beneath  this  orifice  is  fituated  the  opening  of 
the  vagina  itfelf,  environed  by  crypta  of  various 
kinds,  fucli,  for  example,  as  the  urethral  lacuna 
of  Graaf,  and  the  mouths  of  what  are  improperly 
and  even  abfurdly  termed,  the  proilare  glands  of 
Cafp.  Bartholin,  &c,  with  the  unguen-Iike  mucus 

of 


OF  THE  FEMALE  SEX.  135 

of  which,  thefe  obfcene  parts  are  moiftened  and 
lubricated. 

§  533- 
Over  the  very  threshold  or  entrance  of  the 
vagina  is  expanded  a  weblike  production  denomi- 
nated the  hymen.  This  is  a  membrane,  the  exis- 
tence of  which  in  an  unlacerarcd  condition,  is 
confidered  as  a  fure  badge  of  fpotlefs  virginity — 
a  membrane  beftowed  exclufively  on  the  female 
of  the  human  fpecies,  and  of  which  no  phyfical 
deflination  has  been  yet  unequivocally  afcertained. 

The  fringes  or  refidual  fragments  of  this  mem- 
brane, after  laceration,  are  gradually  converted 
into  what  are  denominated  caruncula  myrtiformes9 
bodies  quite  indefinite  in  point  of  number. 

§  534- 
From  the  immediate  feat  of  thefe  minute  myrti- 
form  bodies  afcends,  between  the  urinary  cyfl  and 
inteflinum  rectum,  the  vagina,  a  tube  compofed 
of  a  cellular  parenchyma,  interfperfed  with  an 
infinitude  of  fmall  blood-vefiels.  At  its  inferior 
extremity  the  vagina  is  encircled  by  a  mufcle 
denominated  conftriclor  cunni ;  more  internally  it 
is  lined  by  a  very  (oft  and  delicate  coat,  which  is 
characterifed  by  two  extremely  elegant  columns  of 
ruga  or  wrinkles,  namely,  the  anterior  and  pofie- 
I  4  rio.r ; 


i36  OF  THE  GENITAL  FUNCTION 

rior ;  from  thefe  columns  a  fine  mucus  is  con- 
flantly  difcharged,  deflined  to  lubricate  the  cavity 
of  this  highly  important  canal. 

§  535- 
The  vagina,  at  its  upper  and  interior  end,  re- 
ceives and  embraces,  finally,  the  uterus,  an  organ 
attached  on  each  fide  to,  and  thus  fufpended  by, 
the  Ugammta  laia. 

The  cylindrical  neck  of  this  organ  being  thus 
embraced,  as  it  were,  by  the  vagina,  is  perforated 
by  a  narrow  canal,  which,  like  that  of  the  vagina, 
is  impreffed  by  a  fiiuular  apparatus  or  arrange- 
ment of  rugefirics,  designated  by  the  name  of 
arbor  vit<s  :  of  thi s  canal  the  two  extreme  orifices, 
more  efpecially  the  fuperior  or  internal,  are  over- 
fpreacl,  for  the  mod  part,  with  a  quantity  of  tena- 
cious mucus. 

§  $36- 

The  fubflance  of  the  uterus  is  altogether  fin- 
gular  in  its  nature,  confuting  of  a  peculiar  paren- 
chyma, very  denfe  and  compact,  and  interwoven 
wah  an  infumude  of  blood-vefiels  (running  in 
ferpentine  mazes  of  aitonifhing  intricacy)  of  which, 
the  veins  are  wholly  deftitute  of  valves.  This 
organ  is  doubtlefs  furnifhed,  in  like  manner,  with 
an   apparatus  of  lymphatic   vefTels :    it  abounds 

with 


OF  THE  FEMALE  SEX.  137 

with  a  countlefs  number  of  nerves,  through  the 
medium  of  which,  it  preferves  fuch  a»  aftonifliing 
fympathy  with  the  other  parts  of  the  fyftem. 

§  537- 
Externally  the  uterus  is  invefted  by  the  perito- 
neum, while  its  minute  internal  cavity  is  lined, 
efpecially  at  its  fundus^  by  a  very  foft  and  tender 
membrane,  of  a  fpbngy  texture,  which,  as  fome 
phyfiologifts  allege,  confifts  of  colourlefs  veffels, 
while  others  pronounce  it  to  be  compofed  of  lym- 
phatic abforbents. 

s  538- 

With  regard  to  the  mufcular  texture  attributed 
to  this  organ  by  fome  phyfiologifts,  and  ftrenu- 
cufly  denied  again  by  others,  I  muft  take  the 
liberty  of  obferving,  that  notwithstanding  the 
number  of  uteri  which  I  have  examined  with  the 
utmoft  care  and  attention,  both  in  an  impregnated 
and  an  unimpregnated  (late,  (in  each  of  which  I 
have  had  repeated  opportunities  of  examining  this 
organ,  not  only  in  a  prepared  condition,  but  alfo 
in  fubjecls  recently  dead),  I  have  never  yet  been 
able  to  deteft,  in  them,  any  portion  that  exhibited 
obvious  and  unequivocal  figns  of  mufcularity.  On 
the  other  hand,  I  am  daily  more  and  more  per- 
fcaded,  that  the  uterus,  poiTeffing  no  mufcular 
fibres,  is  deflitute  alfo  of  true  irritability  (§  307), 

and 


tjS  OF  THE  GENITAL  FUNCTION 

and  owe:,  entirely  to  a  vita  propria,  or  fpecifk  life 
(§  47. ),  all  its  peculiar  motions  and  functions, 
which  cannot,  indeed,  with  the  fmalleft  femblance 
of  propriety,  be  derived  from  any  of  thofe  ener- 
gies that  are  common  to  what  we  formerly  term- 
ed the  paries  fimilares^  or  fimiiar  parts  of  the 
body  (§  43,  46).  So  very  fingular  and  unac- 
countable did  the  motions  and  functions  of  the 
uterus  appear  to  the  phyficians  and  phiiefopfv  --. 
of  ancient  times,  that  they  were  led  to  coufidei 
this  organ  as  a  fmaller  animal  contained  within  a 
larger. 

5  539- 

From  the  ancles  on  each  fide  of  the  lacunar- 
or  fundus  uteri,  arife  what  are  called  the  Fallopian 
lubes.  Thefe  are  two  very  narrow  and  tortuous 
canals,  that  run  in  the  fuperior  duplicature  of  the 
ligavienUi  lata  :  they  are  fimiiar  in  texture  to  the 
vagina  iifelf,  except,  that  being  internally  deffitute 
of  valves,  they  are  lined  with  a  kind  of  fpongy 
fiefli,  of  a  very  foft  and  tender  confidence. 

^  §  54°- 
The  extreme  orifices  of  thefe  tubes,  that  regard 
the  abdominal  cavity,  befides  being  much  more 
capacious  than  thofe  which  open  into  the  uterus, 
are  alfo  edged  round  by  fringe  or  finger-like_yf;«- 
J?ria,  of  a  truly  fingular  and  elegant  flruclure. 

The 


OF  THE  EEMALE  SEX.  139 

The  offices  which  thefe  fimbria?  are  deftined  to 
perform,  in  the  bufmefs  of  conception,  appear  to 
be  indeed  of  no  fmall  degree  of  importance  ;  thus 
bein?;  rendered,  during  the  venereal  orgafm, 
equally  turgid  with  the  tubes  themfelves,  they 
evi  lenrly  embrace,  in  this  fcate,  the  ovaria  that 
are  fituated  in  fome  meafure  beneath  them. 

§  54*. 
The  ovaria  themfelves,  or  (he  female  te/ies,  as 

they  were  called  previoufly  to  the  time  of  Steno, 
befides  a  tenacious  and  fomewhat  tendon-like  in- 
volucrum,  confift  alfo  of  a  denfe  and  decuflating 
cellular  membrane,  which  inclofes  in  each  ova- 
rium about  fifteen  of  thofe  minute  bodies  denomi- 
nated the  ovida,  or  little  eggs  of  Graaf :  thefe 
ovula  contain  each  a  fmall  veficle,  or  rather  drop 
of  ferum,  faintly  yellowiih  in  its  colour,  and  of  an 
albuminous  nature,  which,  if  the  recent  ovarium 
be  immerfed  in  boiling  water,  is  reduced,  like  the 
genuine  white  of  eggs,  to  a  ftate  of  complete  co- 
agulation. 

§  542. 
An  albuminoid  drop  of  this  kind  appears  to  be 
indeed  the  principal  fluid  which  the  female  con- 
tributes towards  the  procefs  of  conception  ;  for  it 
appears  extremely  probable,  that,  throughout  the 
progreffive  courfe  of  what  are  termed  the  prime 

or 


f4o    OF  THE  GENITAL  FUNCTION,  fefr. 

or  better  years  of  life,  thefe  final!  drops  arrive  at 
complete  maturity  in  gradual  fucceflion,  fo  that 
each  one,  in  its  turn,  looks  as  it  were  through  the 
involucrum,  by  which  the  ovarium  is  enveioped, 
till  it  is  able  finally  to  burfl  the  parietes  of  its 
prifon,  and  thus  be  received  by  the  abdominal 
orifice  of  the  Fallopian  tube. 

§  543- 
But  befides  this  minute  albuminous  drop  that 
thus  bnrfts  from  the  volume  of  the  ovarium,  it 
appears  that  there  occurs  alfo,  during  the  vene- 
real ceftrum,  an  effufion  of  another  liquor,  which 
ancient  phyfiologifts  very  improperly  and  errone- 
ously denominated  the  female  femen.  Refpecling 
the  nature,  however,  the  fources,  and  the  univer- 
ial  prefence  of  this  humour,  we  are  able  to  pro- 
pcfc  nothing  more  determinate  or  faiisfaftory  than 
we  can  advance  with  regard  to  its  deftination 
and  ufes. 


SECT, 


OF  MENSTRUATION.  141 

SECT.     XLII. 
OF   MENSTRUATION. 

§  544- 

xjl  VERY  frequent  and  highly  import- 
ant function  of  the  uterus  in  the  female  of  the  hu- 
man fpecies  is,  to  difcharge  monthly  a  tributary 
effufion  (called  therefore  caiamema),  during  the 
tedious  and  momentous  term  of  about  thirty  years. 
This  is  a  painful  condition  of  evidence,  to  which 
nature  has  not  fubje&ed  any  other  genus  of  her 
fubje&s,  throughout  the  wide  and  diverfified  range 
of  the  whole  animal  kingdom  ;  fo  that  to  ufe  the 
words  of  the  eloquent  Pliny  "  the  only  mcnjlruous 
"  animal  in  nature  is  woman."  From  this  con- 
dition, on  the  other  hand,  painful  as  it  is,  nature 
has  not  exempted  the  females  of  any  of  the  known 
nations  of  the  globe,  but  has  ftamped  it  with 
the  facred  character  of  an  effential  requifite — of 
a  genuine  fine  qua  ?ion,  in  rendering  the  female 
fex  competent  to  the  propagation  of  their  fpecies. 

§  545- 

The  commencement   of  this  lingular  function 

generally  takes  place,  in  our  climate,  about  the 

fifteenth  year  of  life,  and  is,  for  the  mod  part, 

preceded  by  various  and  unequivocal  fymptoms 

of 


142  OF  MENSTRUATION1. 

of  plethora,  fuch  as  congeftion  and  anxiety  about 
the  bread,  fenfe  of  tenfion  and  weight  in  the  lum- 
bar region,  hffitude  or  wearinefs  of  the  limbs,  &:c. 
Cn  the  firft  appearance  of  the  catamenia,  the  ge- 
nital organs,  in  the  beginning  of  the  attack,  ufu- 
ally  difcharge  a  humour  of  a  pale  reddifh  cad ; 
this  is  gradually  fuceeeded  by  a  liquid  of  a  more 
intenfely  florid  and  finguineous  colour,  which 
terminates,  at  length,  in  an  effufion  of  genuine 
cruor  or  red  blood.  This  fpontaneous,  though 
gentle  difcharge  of  blood,  is  kept  up  for  the 
term  of  feveral  days,  and  is,  in  the  mean  time, 
accompanied  by  a  gradual  ceffation  of  all  thofe 
diftreffing  fymptoms  of  which  we  have  juft  exhi- 
bited a  partial  detail. 

§   546. 

From  the  time  of  its  firfl  occurrence,  this  con* 
ftitutional  hemorrhagy  (as  it  may,  with  fufHcient 
propriety,  be  denominated)  becomes  regularly  pe- 
riodical :  thus  its  future  paroxyfms  return  uni- 
formly about  the  expiration  of  every  fourth  week, 
and  at  each  recurrence,  the  evacuation  continues, 
at  a  mean  calculation,  about  fix  days  j  during 
which  term,  a  healthy  female  is  fuppofed  to  dif- 
charge from  eight  ounces  to  an  entire  pound  of 
blood. 

§  547- 


OF  MENSTRUATION.  143 

§  547- 
It  is  proper,  however,  to  obferve,  that  this  func- 
tion is  fubjeft,  for  the  moft  part,  to  an  entire  in- 
termiffion,  during  the  ftate  of  female  pregnancy, 
and  the  term  of  maternal  lactation. 

The  final  cejfation  of  the  catamenia  occurs  after 
their  difcharge  has  continued,  at  ftated  periods, 
about  the  fpace  of  thirty  years,  which  term  of 
lime  is  completed,  in  our  climate,  about  the  45th 
year  of  life. 

§  548. 
The  fources  of  the  catamenial  dsfciiafge  have 
been  referred  by  fome  to  the  veffels  of  the  vagina, 
and  by  others  (with  fuperior  weight  of  evidence 
on  their  fide)  to  thofe  of  the  uterus :  for  with 
regard  to  thofe  examples  commonly  adduced  in 
fupport  of  the  former  opinion,  where  women, 
although  pregnant,  poffefling  an  imperforated 
uterus,  or  diftrehed  by  a  prolapfus  of  that  organ 
in  "an  inverted  ftate,  have  notwithstanding  men- 
flruated  with  uniform  regularity,  they  tend  to 
prove  nothing  tlfe  than  the  powerful  efforts  of 
the  vis  medicatrix  natures t  which  in  cafes  where 
the  main  llreet  is  obftru&ed,  is  (to  adopt  a  vulgar 
mode  of  expreffion)  fortunately  acquainted  with 
the  routes  through  lanes  and  alleys.  There  are 
on  record,  on  the  other  hand,  numerous  diffe&iom 

of 


r44  of  menstruation: 

of  females  who  died  during  the  term  of  a£hial 
menftruation,  from  which  it  was  unequivocally 
afcertained,  that  the  catamenial  difcharge  had 
been  wept  out  of,  or  difcharged  in  a  flillicidious 
manner  from,  the  uterine  cavity  of  thefe  fubjects  : 
not  to  mention  the  arguments  drawn  a  priori  (as 
metaphyficians  exprefs  themfelves),  from  which  it 
appears  highly  probable,  that  the  end  and  deto- 
nation of  the  menfes  are,  to  prepare  the  uterus 
for  a  date  of  future  pregnancy,  and  render  it  more 
fit  for  the  regular  nutrition  of  the  foetus.  For 
the  very  fame  reafons  alfo  this  hemorrhagy  ap- 
pears to  be  attributed,  with  more  propriety,  to 
the  arterial  than  to  the  venous  veffels  of  the 
uterus. 

§  549- 
With  regard  to  the  caufes  of  this  periodical  and 
perennial  hemorrhagy,  they  are  ftirouded  by  fo 
thick  a  curtain  of  obfeurity,  and  their  invefligation 
is  attended  with  fuch  momentous  difficulties,  that 
in  the  profecuticn  of  this  fubjecl,  we  have  not  a 
fufficient  power  of  evidence  to  conduct  us  over 
the  arduous  mound  which  divides  the  twilight- 
region  of  probability  from  the  more  luminous  realm 
of  demonjl ration^  and  certainty. 

The  proximate  caufe  phyfiologifts  fuppofe  to  be 
a  certain  topical  congeflion  or  plethora,  to  which 

i  opinion, 


OF  MENSTRUATION.  145, 

opinion,  indeed,  the  fymptoms  of  the  impending 
catamenia,  together  with  the  profufion  and  nature 
of  the  uterine  blood-veffels  fitly  enough  correfpond, 
and  in  favour  of  the  truth  of  which  they  exhibit 
a  degree  of  teftimony  fufficiently  refpectable. 

Among  its  remote  caufes  it  will  be  proper  to 
enumerate,  the  ereft  pofition  of  the  body  (a  pofi- 
tion  that  ferves  as  a  char acleri flic  diftinttion  be- 
tween the  human  fpecies  and  moil  other  defcrip- 
tions  of  animals)  ;  to  which  we  mud  add,  the 
fmgular  parenchyma  of  the  uterus  itfelf,  and, 
finally,  the  vita  propria  or  fpecific  life  of  that 
important  organ. 

With  regard  to  the  caufe  of  the  periodical  re- 
currence of  the  catamenia,  it  will  here  be  better, 
much  better  to  acknowledge  our  ignorance,  than 
to  indulge  ourfelves  in  vague  and  vifionary  con- 
jectures, and  fportively  range  through  the  fair  but 
fallacious  fields  of  mere  fpeCulative  hypothefis. 
For  I  am,  indeed,  perfuaded,  that  all  thofe  peri- 
odical phenomena  which  occur  in  the  animal  body, 
whether  in  health  or  difeafe,  (provided  their  in- 
terval extend  beyond  the  term  of  24  hours)  mud: 
be  ranked  with  thofe  latent  myjleries  of  animal 
nature,  which  nothing  but  time;  talents,  and  in- 
duftry,  will  be  ever  able  to  develope. 

vol.  11.  K  SECT. 


i4<6  OF  THE  MILK. 

SECT.     XLIII. 
OF  THE  MILK. 

§  55°- 

JjETWEEN  the  female  mamma  and 
uterus  (the  former  of  which  were,  by  the  philo- 
fopher  Favorinus  in  his  communications  to  Gellius, 
elegantly  and  emphatically  denominated,  the  fa- 
cred  fountains  that  nouriJJj  the  human  race,  there 
exifts  fuch  an  extremely  potent  fympathetic  con- 
ne£tion,  that  thefe  two  organs  may  be  faid  to  be 
iiidiiTolubly  aifociated,  or  to  accompany  each  other 
hand  in  hand,  in  their  phenomena  and  functions. 
Thus,  during  the  tender  period  of  infancy,  fo 
great  is  their  imbecility  and  want  of  action,  that 
they  are  capable  of  performing  fcarcely  any  func- 
tion at  all :  as  the  years  of  puberty  advance, 
they  begin,  at  the  fame  time,  to  acquire  vigour 
and  activity,  fo  that  on  the  firft  eruption  of  the 
catamenia,  a  fwclling  of  the  mamma?  or  breads 
mes  alfo  evident  to  the  fenfes.  Throughout 
riie  fubfequent  periods  of  life  thofe  two  organs 
are  either  fubjectcd  to  fimultaneous  and  fimilar 
changes,  as  when  the  breads  become  turgid  and 
difcharge  mil!:  during  the  progrefs  of  pregnancy  ; 
or  experience  alternate  and   oppofite  aifeftions, 

inftances 


OF  THE  MILK.  147 

inftances  of  which  we  have  in  the  fufpenfion  of 
the  catamenia  during  the  term  of  lactation,  a  more 
copious  effullon  of  the  lochia  when  the  fecretion. 
of  milk  does  not  commence  at  the  ufual  period, 
§cc.  And,  laftly,  on  the  unwelcome  acceffion  of 
old  age,  both  the  preceding  functions  fail  at  the 
fame  time,  fo  that  when  the  catamenia  finally 
retreat,  never  again  to  return,  the  uterus  and 
mammae  become  equally  flaccid,  inert  and  wholly 
incapable  of  their  former  action.  A  great  variety 
of  pathological  phenomena,  eafily  obfervable  in 
cafes  of  irregular  menflruation,  mfltfor  albus,  and 
other  fimilar  affections,  (hall  be  in  filence  preter- 
mitted, although  they  furnifh  the  molt  potent  and 
unequivocal  teftimony  in  confirmation  of  the 
fympathy  now  finder  consideration,  namely,  that 
which  exifls  between  the  uterus  and  mammas. 

§   S51- 

Nor  will  this  intimate  fympathetic  connection, 
which  fublifts  between  the  uterus  and  ma  ma?, 
appear  in  any  meafure  extraordinary  or  furprifing, 
when  we  confider,  that  all  thofe  diveriified  jburces 
of  phyiiological  confent,  particularly  enumerated 
on  a  former  occafion  (§  54),  jointjy  co-operate  in 
the  eflablimment  of  fuch  connection  between  thefe 
organs  of  the  female  thorax  and  abdomen. 

K  2  §  552. 


t48  OF  THE  MILK. 

The  anaftomofis  obfervable  between  the  internal 
mammary  and  epigaftric  arteries,  was  formerly 
efteemcd  a  circumftance  of  the  higheft  importance 
in  the  explication  of  the  foregoing  confent.  Al- 
though phyfiologifts  have  hitherto  attributed  by 
far  too  much  to  this  remarkable  anaftomofis,  yet 
that  it  ought  not  to  be  entirely  excepted  from  the 
number  of  co-operating  caulks  will  appear  ex- 
tremely probable  to  any  one  who  confiders  the 
obvious  and  wide  difference  which  exifts  between 
the  diameter  of  the  epigaftric  artery  in  a  (late  of 
pregnancy,  and  that  of  the  fame  vefTel  during  the 
period  of  laclation. 

§  553- 
The  two  preceding  organs,  namely,  the  uterm 

and  mammae,  pofTefs  alfo,  in  common  with  each 
other,  this  further  property,  that  they  both  retain 
and  exhibit  a  friendly  affinity  or  attraction  for  the 
chyle,  by  which  means  they  folicit  that  fluid  to 
themfelves,  efpecially  during  the  term  of  preg- 
nancy, and  thus  convert  it  to  peculiar  ufes. 

§  554- 
The  female  mamma?  confifts  of  a  placentoid  con- 
geries of  fmall  conglomerate  glands,  diftinguiflied 
by  numerous  Juki  into  lobes  of  confiderable  mag- 
nitude,  and  completely  embedded  in  a  mafs  of 

adipofe 


OF  THE  MILK.  149 

adipofe  fubftance.  On  the  anterior  part,  in  particu- 
lar, a  protuberance  is  formed  by  a  more  firm  feba- 
cious  cufhion,  which  is  covered  and  protected  by 
a  cutis  of  a  very  tender  and  delicate  texture. 

S  555- 
Each  one  of  thefe  lobes  is  compofed  of  a  num- 
ber of  inferior  lobuli,  and  thefe  a^ain  of  what  are 
denominated  acini  or  kernels,  in  which  the  incipi- 
ent radicles  of  the  lacliferous  duels  originate,  and 
from  the  extreme  ra?nuli  or  branches  of  the  in- 
ternal mammary  artery  extract  a  chyliform  fluid, 
which  they  are  particularly  deflined  to  convey. 

§556- 

Tb?  fine  filiform  radicles  uniting  fucceffively 
in  their  onward  palfage,  terminate  finally  in  lead- 
ing trunks,  correfponding  in  number  to  the  prin- 
cipal lobes  ;  fo  that  they  generally  amount,  in 
each  mamma,  to  about  fifteen  or  perhaps  a  few 
more.  Thefe  trunks  are  frequently  dilated  into 
more  fpacious  finufes,  but  never  appear  to  be  con- 
nected by  genuine  anaftomofes. 

§   557' 

Thefe  trunks  terminate  in  excretory  canals  of 

exquifite  delicacy   and   tendernefs,  which,  being 

collected  and  clofely  approximated  towards  the 

centre  of  the  mamma,  form,  by  the  co-operation 

K  3  of 


150  OF  THE  MILK. 

of  cellular  membrane,  the  patilla  or  nipple.  This 
projecting  papilla  being  interfperfed  and  minutely 
pervaded  by  an  infinitude  of  blood-veffels  and 
nerves  of  extreme  finenefs  and  fubtlety,  is  ful  je£l 
to  a  very  Angular  fpecies  of  erection  on  the  accef- 
fion  of  certain  external  (limuli. 

§  558. 

The  nipple  is  furrounded  by  an  areola  or  fmall 
circle,  which  is  confpicuous,  as  well  as  the  pa- 
pilla itfelf,  on  account  of  the  fingular  colour  of 
the  reticulum  mucofum  expanded  immediately  be- 
neath the  epidermis  or  cuticle.  This  areola  is 
further  diftinguifhed  by  fmall  ftbaceous  follicles, 
and  likewife  by  a  few  minute  lactiferous  ducts  with 
which  it  is  in  fome  inllances  pervaded. 

§  559- 

The  human  mV.h  which  is  fecreted  in  the  glan- 
dular organs  hi  frert'o  defcribed,  is  a  fluid  of  a 
well  known  coloiir,  fomewhat  watery,  and  con- 
taining alfo  a  fmall  portion  of  oil  :  this  liquid  is 
fweetilh  to  the  t  ;fte,  extremely  mild,  and  refem- 
bles,  in  its  general  properties,  the  milk  of  do- 
meftic  animals  belonging  to  the  clafs  mammalia, 
except  that  it  is  nor,  like  the  latter,  fubjtel  to  co- 
agulation from  the  action  of  acids,  nor  does  it  ex- 
feifcit,  to  the  moll  attentive  obfervation,  the  flight- 
eft  veflige  of  volatile  alkali. 


OF  THE  MILK.  151 

When  coagulated,  however,  by  the  influence 
of  fpirits  of  wine,  it  exhibits  the  fame  component 
elements  of  which  the  milk  of  thofe  other  animals 
already  mentioned  is  known  to  coniifl.  For  be- 
sides the  watery  halites  which  human  milk  emits 
when  recently  drawn,  and  yet  in  a  tepid  (late,  its 
Jerum,  feparating  from  the  cafeous  or  cheezy  por- 
tion, contains  alfo  the  fugar  of  milk,  which  is 
compofed  of  the  faccharine  acid  united  to  a  calca- 
reous earth,  together  with  certain  additional  parts 
oily  and  mucaginous  in  their  natures.  Laftly,  it 
contains  alfo  a  crtam  or  butter-like  portion,  the 
globules  of  which  are*  extremely  various  and 
changeable  in  their  magnitudes,  ihus  vibrating  in 
their  diameters  from  the  TJ.th  to  the  »2vth  part 
of  a  line. 

^  561. 

The  analogy  which  is  obferved  to  exifl  between 
chyle  and  blood,  and  between  each  of  thefe 
liquids  and  milk  itfelf,  renders  it  fufliciently  pro- 
bable, that  this  laft  humour,  (which  conttitutes 
at  prefent  the  more  immediate  object  of  our  con- 
fideration),  is  a  fpecies  of  chyle  renovated  from 
the  volume  of  b/osd,  or  rather  feparated  from  this 
crimfon  fluid  (with  which  it  had  jufl  formed  a 
'junction)  previouily  to  its  final  and  complete  afli- 
milation.  This  opinion,  befides  other  arguments 
K  4  win 


r  r 


1 52  OF  THE  MILK. 

which  might  be  advanced  in  its  favour,  derives 
powerful  testimony  from  the  fpecific  taftes  of  feve- 
ral  kinds  of  aliment  being  not  unfrequently  per- 
ceptible in  the  milk  of  nurfes ;  and  alfo  from  the 
chyle-like  habit  and  conftitution  of  that  watery 
milk,  which  not  unfrequently  exudes  from  the 
breafts  of  females  during  the  term  of  pregnancy, 
and  for  a  fhort  time  after  the  period  of  parturition. 

§  5^2. 
The  reafon  why,  during  the  progrefiive  con- 
tinuance of  lactation,  this  bland  food  of  the 
foetus  becomes  gradually  more  and  more  infpif- 
fated,  rich  and  oily,  mufl  be  referred  chiefly  to 
the  lymphatic  veins,  with  which  the  mammae 
plentifully  abound  :  Thus  the  more  profufe  the 
afflux  of  milk,  and  the  greater  length  of  time  this 
afflux  has  continued,  with  the  more  power  and 
uniformity  do  thtfe  lymphatics  abforb  its  ferous 
parts,  and  convey  them  back  to  the  mafs  of  cir- 
culating blood,  by  which  means  they  furnifh  the 
moil  effective  aid  to  the  whole  procefs  of  this  fe- 
cretion  (§  476). 

§    563- 

During  the  firft  days  after  parturition,  a  very 

profufe  fecretion  of  milk  occurs,  and   (provided 

the  mother  /aflates,  i.  e.  fuckles  her  child)  is  pro- 

*  moted  and  kept  up  by  the  faction  of  the  infant 

itfelf, 


OF  THE  MILK.  153 

itfelf,  Until  i-he  catamenia  return,  which  had  for 
a  long  lime  ceafed  to  flow  (^  547).  The  exig- 
ence of  milk  in  the  breads  of  virgins  truly  invio- 
late, in  the  breads  of  new-born  infants  of  each 
fex,  and  even  in  the  breads  of  men  themfelves, 
as  well  as  in  thofe  of  other  male  animals  belong- 
ing to  the  clafs  mammalia,  is  a  phenomenon  which 
not  unfrequently  prefents  itfelf  to  our  obfervation. 

§   564- 

A  profufe  quantity  or  accumulation  of  milk  in 
the  breads  effectually  fohens  its  own  final  excre- 
tion, whence  a  fpont  neous  difcharge  of  that  fluid 
is  obferved  frequency  to  occur  ;  this  difcharge 
is  further  promoted  by  the  external  preflure  of 
the  marnmce,  as  well  as  by  the  faction  of  the 
tender  infant. 


SECT. 


154  OF  CONCEPTION 

SECT.     XLIV. 
OF  CONCEPTION  AND  PREGNANCY. 

§    565. 


AVING  hitherto  confident!  the 
ftrufture  of  the  genital  organs  peculiarly  belong- 
ing to  each  fex,  we  come  now  to  treat  of  thofe 
functions  or  proceffcs  which  conftitute  the  imme- 
diate end  and  destination  of  thefe  organs,  namely, 
conception  and  the  propagation  of  the  human  race. 
In  the  order  and  progrefs  of  our  enquiries  into 
thefe  abflrufe  and  interefting  fubje&s,  we  will  firhV 
give  a  plain  and  fimple  narrative  of  the  feveral 
phenomena  obfervable  in  this  admirable  and  truly 
divine  procefs ;  and  then  attempt  an  inveftigation 
of  the  energies  from  which  thefe  phenomena 
appear  to  originate. 

§   566. 

It  is,  in  the  firfl  place,  neceffary  to  obferve, 
that  the  fubjetls  of  the  human  race  have  not,  like 
mod:  other  animals  (all  thofe,  if  I  be  not  deceived, 
belonging  to  the  clafs  mammalia,  man  alone  ex- 
cepted), any  peculiar  feafon  of  the  year  in  which 
they  are  unufually  prone  to  venereal  enjoyments, 

but 


AND  PREGNANCY.  155 

but  are  equally  liable  to  experience,  at  every  pe- 
riod and  under  every  varying  temperature,  the 
gentle  glow  of  love's  diffufive  fires. 

§   567- 

When  therefore,  the  female  of  the  human  fpe- 
cies  a  ;m.ts  rhe  embraces  of  the  male,  and  while 
they  are  thus  mutually  enwrapt  in  the  ardour  of 
th.u  animal  inlfinct.  which  far  furpafTes  every  other 
both  in  the  univerfaliiy  and  the  potency  of  its  fway, 
the  uterus  (if  we  be  not  greatly  dectived)  being 
rendered  turgid  by  a  fpecies  of  inflammatory  or- 
gafm,  and  animated   at  the  fame  time  by  its  own 
fpecifie   life,  (§  538.)  drinks  in,   as  it  were,  the 
feminai  fluid  emitted  by  the  male,  and  effects  a 
fvnehronous  difcharge  of  that  which  is  proper  to 
itfeh  (§  543)  ;   the  fallopian  tubes  become  at  the 
fame  time  rigid,  and  with  their  fimbricated  extre- 
mities embrace  the  adjacent  ovaria  :   in  one  or  the 
other  of  thefe  ovaria  one  of  the  veficula?  GraafRante 
is  lacerated  or  burn1,  fomewhat  after  the  manner 
cf  an  abfeefs  advanced  to  a  (late  of  complete  ma- 
turity, and  the  albuminoid  liquid  which  this  rup- 
tured veficula  contained,   being  abforbed  by  the 
orifice  of  the  embracing  tube,  is  thus  conveyed 
onward  into  the  cavity  of  the  uterus. 

§  568. 


1)5  OF  CONCEPTION 

§568. 
This  liquid  being  difcharged  from  the  ovary, 
ihe  external  lips  of  the  final  1  and  recent  wound 
through  which  it  was  emitted,  are  again  united 
by  a  fine  cicatrix,  while  the  remaining  delicate 
vafcular  membrane  in  which  the  liquid  had  been 
enclofed,  conrtitutes  what  is  called  corpus  luteian. 
This  body  appears  to  be  at  firft  hollow  and  filled 
with  a  quantity  of  plallic  lymph,  that  in  procefs 
of  time  is  converted  into  a  flefhy  nucleus,  inverted 
by  a  firm  cortex  or  membrane,  which  is  inter- 
fperfed  by  a  variety  of  minute,  yet  remarkable 
blood-veffcls. 

§  5^9- 
The  uterus  being  thus  impregnated,  the  canal 
leading  through  the  cervex  or  neck  of  that  organ, 
efpecially  towards  its  fuperior  or  internal  orifice, 
(§  535-)  ls  completely  obftructed,  in  fuch  a  man- 
ner, that  according  to  the  common  courfe  of 
nature  there  is  no  room  left  for  fuperfcetation. 

§  57°- 
The  internal  fuperfices  of  the  uterus  appears  to 

be  inverted  with  a  flight  inflammatory  cruft  of 

plaftic  or  coagulable  lymph,  (§  19.)  which  forms 

the  membrana  caduca,  (called  alfo  membrana  de- 

eidua),  of  Hunter. 

This 


AND  PREGNANCY.  157 

This  membrane-like  cruft  phyfiologifts  diflin- 
guifli  into  two  laminse  or  layers;  one  of  which, 
denominated  lamina  crajfa,  inverts  the  whole 
internal  cavity  of  the  uterus,  except  the  imme- 
diate openings  into  the  fallopian  tubes,  and  the 
internal  orifice  of  the  cervical  canal;  while  the. 
other  is  the  growth  of  a  later  period,  and  appears 
to  be  generated  in  the  following  manner,  viz. 
after  the  formation  of  the  ovulum  is  fairly  com- 
menced, and  this  miuute  body  begins  to  ftrike  its 
roots  into  the  decidua,  already  mentioned,  this 
fecond  lamina  begins  gradually  to  expand,  and  is 
thus  continued  from  the  place  where  thofe  minute 
roots  begin  to  pullulate,  over  the  remaining 
fuperficies  of  the  ovum,  whence  it  has  been 
diftinguilhed  by  the  name  of  caduca  reficxa. 

§    571- 

Although  the  ovulum  be  formed  itfelf  at  an 
earlier  period  than  the  embryo  which  it  is  deftined 
to  contain,  yet  the  real  organization  of  the  former 
feldom  commences  earlier  than  the  termination  of 
the  firft  week  after  conception.  For  I  very  much 
doubt,  whether  or  not,  at  an  earlier  period  than 
this,  any  unequivocal  veftige  of  an  organifed  body 
has  been  ever  obferved  in  the  impregnated  uterus 
•f  the  human  fubjeft. 

S  57*< 


158  OF  CONCEPTION. 

§  572- 
This  ovulum,  or  little  egg,  is  compofed  of  two 
proper  membranes,  befides  that  external  adven- 
titious covering,  which  it  derives  from  the  caduca 
of  Hunter. 

The  proper  membranes  are,  firft,  an  external 
one,  apparently  deftitute  of  bloo.l  vcffcls,  which 
forms  the  chorion  of  modern  writrrs.  From  the 
earlieft  origin  of  this  membrane  :;  great  part  <  f  its 
external  fuperficies  is  beautifully  f  t  with  kn  t  like 
flocculi  or  minute  piles  of  inconreiv  •  'e  elegance, 
from  whence  it  has  been  called,  chorion  mufeofum 
feu  frondofum,  i.  e.  the  mo fs -like,  or  leaf-like, 
chorion.  By  means  of  thofe  delicate  piles,  which 
conftitute  the  rudiments  of  the  foetal  part  of  t  e 
future  placenta,  the  ovulum  is  inferted  (as  if  by 
roots)  into  the  decidua  uterina.     (§  569. J 

The  other  membrane,  lying  interiorly,  is  deno*- 
minated  the  amnion,  which  is  alfo  defliture  of 
blood-vefTels,  (§  5.)  it  is  indeed  delicate  and  ten- 
der, but  yet  of  remarkable  tenacity  and  ftrength. 

§   573' 
For  a  few  weeks  after  the  firfl  formation  of  the 

ovulum,  its  two  proper  membranes  differ  v<ry 
widely  from  each  other  in  point  of  fize,  the 
chorion   exhibiting  the  appearance   of  a   larger 

bladder, 


AND  PREGNANCY.  159 

bladder,  to  the  infide  of  which  the  amnion 
adheres  under  the  form  of  a  /mailer  one,  and  is 
attached  in  particular  to  that  part  which  is 
oppofite  to  the  centre  of  the  external  floccofe 
fuperficies  of  the  chorion. 

The  interftice  which  then  exifts  between  the 
chorion  and  amnion  is  filled  with  a  very  fnbtle 
chryilaline  water,  of  doubtful  origin,  and  tranfient 
continuance. 

For  when  the  amnion  begins,  during  the  firffc 
months  after  conception,  to  increafe  with  greater 
rapidity  tkin  the  chorion,  and  to  gain  on  the 
latter  mem1  rane  in  point  of  magnitude,  this  chryf- 
taline  liquor  mud  neceilarily  undergo  a  fynchro- 
nous,  and  perfectly  correfpondent,  diminution. 

S  574- 

The  internal  membrane  of  the  ovum,  from  the 
earlied  period  of  its  formation  (§  570),  till  the 
final  clofe  of  parturition  itfelf,  is  conftantly  filled 
with  a  fluid,  denominated  by  phyfiologifts,  liquor 
amnii.  This  liquid  is  aqueous,  and  of  a  pale 
yellowifli  colour;  it  emits  icarcely  any  odour,  and 
is  to  the  tafte  bland,  with  a  flight  faline  impreg- 
nation hardly  perceptible;  phyfiologifts  generally 
fuppofe  it  to  be  a  fource  of  nourifhment,  and 
compare  it  to  the  white  of  an  egg;,  from  which  it 

notwithstanding, 


:do  OF  CONCEPTION 

notwithstanding,  differs  in  a  very  obvious  and 
efLntial  manner,  as  may  be  eafily  >U  monftrated  by 
an  attentive  experimental  inveftigation. 

The  fources  of  this  fluid  are  as  yet  doubtful:  It 
is  certainly,  however,  neither  derived  from  the 
fcetus  nor  the  urn  ti'ical  cord,  as  it  is  not  unfre- 
quenily  found  in  abortive  ovula,  which  contaiu 
neither  of  thefe  bodies. 

The  quantity  of  this  fluid  is  in  an  inverfe  pro- 
portion to  the  bulk  of  the  foetus.  Thus  the 
fmaller  and  more  tender  the  embryo,  the  more 
profufe  is  the  volume  of  liquor  amnii,  and  vice 
verfa. 

Hence  we  are  at  liberty  to  hazard  a  conjecture 
refpe&ing  the  primary  life  of  ti.is  liquor,  which 
appears  to  be  fubfervienr,  not  fo  much  to  the 
nutrition,  as  to  the  protection  and  defence  of  the 
minute  body  of  the  tenckr  embryo,  as  yet  in  a 
gelatinous  flare,  and,  therefore,  wholly  unable  to 
bear  the  violence  of  external  injuries.  With 
:£l  to  that  fmall  portion  of  the  liquor  anmii, 
which  has  been  fometimes  (though  fo  rarely  as  to 
deferve  to  be  efleemed  a  preternatural  occurrence) 
found  in  the  fiomach  of  the  foetus,  it  cannot 
poflibly  be  deflined  for  the  purpofe  of  its  nutrition, 
as  will  be  obvious  to  any  one  who  confiders  how 
2  extremely 


AND  PREGNANCY.  161 

extremely  inert  and  empty  the  chyliferous  fyftem 
of  even  a  more  mature  foetus  appears,  Low  unfit 
for,  and  even  how  averfe  from,  the  arduous  and 
important  procefs  of  cl  ylification.  To  the  forego- 
ing circumfiances  we  might  (if  necefTary)  fubioin 
various  examples  of  fcetufes  deftitute  of  heads, 
with  diverfe  other  arguments  of  a  flmilar  nature, 
and  tending  to  the  eilabliiliment  of  a  fimilar  refult. 

§  57S- 
The  embryo  itfelf,   which   (fufpended   by  the 

umbilical  cord,  as  fruit  appended  to  its  foot-ftalk), 

floats  in  this  liquor,  begins  to  be  formed  about 

the  third  week  after  conception  :   it  appears  firft 

under  the  very  fimple  globe-like  figure  of  a  final! 

bean  or   kidney,   to  which  the  rudiments  of  the 

extremities  are  gradually  fubjoined,  the  fymmetry 

and  fpecific  form  farther  completed,  &c. 

§    576' 
According  to  the  ufual  courfe  of  nature,  the 

female  of  the  human  fpecies  is  uhiparous,  and  con- 
ceives only  one  foetus  at  a  time.  She  not  un fre- 
quently, however,  bears  twins,  the  proportion  of 
which  to  folitary  births  is,  according  to  the  calcu- 
lations of  SufTmiich,  as  one  to  feven.  In  a  cafe 
of  twins  each  foetus  has  its  own  amnion,  but  they 
are  both  enveloped  in  a  common  chorion. 

vol.  if.  L  Thar 


1 62  OF  CONCEPTION 

S  577- 
That  medium,  by  the  aid  of  which  a  recipro- 
cal intercovirfe  is  preferred  between  the  embryo 
and  mother,  are  the  umbilical  cord,  and  the  pla- 
centa through  which  this  cord  is  minutely  dif- 
tribured. 

§  578- 

The  umbilical  cord,  which  appears  to  be  co- 
eval with  the  embryo  itfelf,  is  indeed  very  ftrik- 
ingly  diverfified,  not  only  in  point  of  length  and 
thicknefs,  but  alfo  with  refpect  to  the  place  of 
its  infertion  into  the  placenta,  its  varicoie  protu- 
berances, &c.  In  general,  however,  it  is  formed 
of  the  fpiral  contortions  of  three  blood-vefiels, 
namely,  a  vein  running  to  the  liver  of  the  fcetus, 
and  two  arteries  which  originate  from  the  inter- 
nal iliacs  or  hypogaflrics.  Thefe  vefTels  are  fe- 
parated  and  diftinguifhed  from  each  other  by  cel- 
lular partitions,  running  in  various  directions,  and 
have  their  lights  or  diameters  frequently  flraitened 
by  the  fmall  nodes  or  valve-like  bodies  of  Ho- 
boken. 

Thefe  veffcls  are  collected  and  compacted  to- 
gether into  a  cord  by  means  of  cellular  membrane, 
which  being  filled  with  a  lingular  and  very  limpid 
humour,  exhibits  the  appearance  of  jelly,  but  is  in- 
veiled  externally  by  a  continuation  of  the  amnion. 

S   579' 


AND  PREGNANCY.  163 

§  579- 
At  the  place  where  the  fetus  is  attached  to 
this  cord,  the  latter  is  joined  by  a  peculiar  body, 
which  originates  from  the  bottom  of  the  vefica 
urinaria  (§  486.),  and  purfues  a  middle  courfe 
between  the  two  umbilical  arteries,  namely,  the 
urachus.  This  body  is,  in  the  human  fpecies, 
pervious,  for  at  lead  a  {hort  fpace,  and  afterwards 
totally  difappears  ;  but  in  other  animals  belong- 
ing to  the  clafs  mammalia,  leads  onward  to  what 
is  called  the  allaniois.  Of  this  allantois  the  human 
foetus  appears  to  be  entirely  deftitute,  unlefs  we 
be  inclined  to  defignate  by  this  name  that  myfte- 
rious  and  tranfient  veficuia  umbiiicalis,  uniformly 
obfervable  in  the  human  ovula,  between  the  cho- 
rion and  amnion,  which  (if  I  be  not  greatly  de- 
ceived) Ifbr.  de  Diemerbroek  firil  difcovered  long 
before  it  was  feen  by  Albums  or  Zinn.  But  in 
more  modern  times  it  is  difcovered  too  frequently, 
and  with  too  uniform  an  afpe£l  in  unvitiated  and 
fruitful  human  ovula,  (even  to  fo  late  a  period  as 
the  third  month  after  conception),  to  be  any 
longer  confidered  as  an  accidental,  a  morbid,  or 
amonftrous  conformation  of  the  part. 

§   580. 

The  blood-vefTels  of  the  cord,  of  which  we 

have  already  fpoken,  pafs  into  the  placenta,  which 

was  formerly  faid  to  originate  from  the  leaf-like 

L  2  fuperficies 


ftf-4  OF  CONCEPTION 

fuperficics  of  the  chorion,  a  membrane  attached 
to,  and  even  inferted  in,  the  dccidua  craffa  : 
Hence  we  perceive  that  the  placenta  is  a  body 
compofed  of  two  different  kinds  of  fubftance,  re- 
ceived from  an  equal  number  of  fources.  Thus, 
for  example,  one  kind  called  the  uterine,  from  its 
immediate  apportion  to  that  organ,  is  derived 
from  the  decidua,  and  conftjtntes  the  fpongy  pa- 
renchymatous portion  of  the  placenta;  while  the 
ether  belonging  to  the  foetus-,  and  therefore  call- 
ed, the  fatal  part,  is  derived  from  the  umbilical 
vefTels  distributed  throughout  the  chorion. 

At  this  time  the  increafe  of  the  tender  ovum 
is  unequal,  fo  that  the  growth  of  the  fmooth  por- 
tion of  the  chorion  is  greater  and  more  rapid 
than  that  of  the  mufecfum  or  mofs-like ;  hence 
it,  is  evident,  that  the  relative  magnitude  of  the 
placenta  to  that  of  the  whole  volume  of  the  egg, 
is  greater  in  proportion  as  the  conception  is  more 
recent*  and  lefs,  on  the  other  hand,  accordingly 
le  period  of  parturition  is  nearer. 

As  pregnancy  gradually  advances,  the  placenta 
becomes  more  and  mere  clofe  and  compact  in  its 
texture;  it  is  impreffed  with  grooves,  and  diftjn- 
hed  into  lobes  on  its  external  furface  which 
refpects  the  u:cru:.,  bnf  is  fmooth  and  highly  po- 
lifiied  on  its  internal,  which,  looking  towards  the 

tus, 


AND  PREGNANCY.  165 

foetus,  is  invelted  or  lined  by  the  amnios.  Witfe 
regard  to  magnitude,  thicknefs,  figure,  and  fitua- 
tion  or  point  of  cohe/ion  to  the  uterus,  it  is  fub- 
jec!  to  a  multitude  of  diverfities ;  it  is  attached, 
however,  for  the  moft  part,"  to  the  fundus  or  bot- 
tom of  that  organ  ;  and  is,  upon  the  v  hole, 
equally  destitute  of  both  feniibiiity  (§  205.)  and 
genuine  irritability  (§  307). 

§  581. 

Although  all  phyiiologiih  uniformly  concur  in 
this,  that  the  placenta  is  the  principal  organ 
through  the  medium  of  which  the  tender  foetus 
is  fupplied  with  nutriment,  yet  various  contro- 
verlies  have  latterly  exifted  among  them  refpect- 
ing  the  genuine  mode  of  its  ofticial  action,  and  its 
reciprocal  relation,  as  well  to  the  uterus  as  to  the 
foetus.  From  an  attentive  and  impartial  confide- 
ration  of  all  the  tetlimony  that  can  be  collected 
on  this  fubjecl,  the  refult  appears  to  be,  that  there 
exifts  no  dirccl:  anaftomofis  between  the  blood- 
veffe'.s  of  the  maternal  uterus  and  thofe  of  the 
umbilical  cord  ;  but  the  arterial  blood  which  paffes 
by  a  continuous  route  from  the  uterus  of  the 
mother  to  that  portion  of  the  placenta  that  owes 
its  origin  to  the  decidua  craiTa,'  is  there  abforbed 
by  the  incipient  radicles  of  the  umbilical  veins, 
that  are  distributed  throughout  the  mofs-like  por- 
tion of  the  chorion,  and  thus  conducted  into  the 
L  3  venous 


1 66  OF  CONCEPTION 

venous  trunk  of  the  funis  umbilicalis  :  while,  on 
the  other  hand,  the  blood  which  is  conveyed 
back  from  the  fceius  by  the  umbilical  arteries, 
being  in  like  manner  effufed  into  the  parenchyma 
of  the  placenta,  is  taken  up  by  the  venous  radi- 
cles of  its  uterine  portion,  and  thus  finally  re-con- 
veyed into  the  fubftance  of  the  uterus  itfelf. 

The  foregoing  opinions  receive  additional  con- 
firmation from  the  many  well  guarded  but  fruit- 
lefs  attempts  that  have  been  made  by  different 
phyfiologiils  to  inject,  the  veffels  of  the  umbilical 
cord  through  thofe  of  the  uterus,  or,  on  the  other 
hand,  to  fill  the  veffels  of  the  latter  organ  by  in- 
jections forced  through  thofe  of  the  former.  As 
a  further  evidence  in  fupport  of  the  fame  prin- 
ciples, we  may  mention  the  difference  which  is 
obferved  to  exift  between  the  pulfe  of  the  mother 
and  that  of  the  foetus  before  their  final  difen- 
gagement  from  each  other;  and  laftly,  it  may 
not  be  improper  to  add,  as  a  circumflance  tend- 
ing to  the  eftablifhmcnt  of  the  fame  rcfulr,  the 
obfervations  which  we  formerly  delivered  refpecl- 
ing  the  difference  between  the  nature  of  the 
fceral  and  that  of  the  maternal  blood  (§  147). 

But  further,  it  appears  probable  that  a  portion 
of  chyle  is  alio  conveyed  to  the  foetus  along  with 
the  blood  of  the  mother.  For  befides  the  confide- 

ration3 


AND  PREGNANCY.  167 

ration,  that  the  blood  of  the  mother  is  not  at  all 
times  equally  pure  and  unmixed,  bur,  for  fome 
hours  after  every  meal,  carries  along  with  it,  in 
an  unafiimilated  ftate,  that  portion  of  chyle  re- 
cently received  from  the  thoracic  duel,  it  has 
been  demonilrated,  on  a  former  occafion,  that  the 
uterus  itfelf  polTeffes  a  fmgular  and  ftrong  affinity 
to  the  chyle  and  milk  (§  550.  SS3-)'f  anc*  tnere 
are  alfo  on  record  a  great  variety  of  obfervations, 
from  which  it  appears,  that  a  milky  juice  has  been 
actually  difcovered  in  the  uterine  portion  of  the 
placenta. 

§  582. 

During  the  progreflive  advancement  of  preg- 
nancy, while  the  foetus  and  fecundities  increafe  fo 
very  remarkably  in  magnitude,  it  is  obvious  that 
the  uterus  mud  be  alfo  fubjected  to  ftriking  and 
remarkable  changes.  Befides  the  augmentation 
of  its  bulk,  fo  extremely  evident  at  firft  view, 
thofe  changes  refpect  alfo  its  fiiuation  and  figure, 
but  affeel:  more  efpecially  the  texture  of  this  An- 
gular and  important  vifcus.  Thus,  in  confequence 
of  the  uniform  and  weighty  congeftion  of  humours 
which  the  gravid  uterus  is  obliged  to  fuflain,  it 
is  likewife  fubjetfted  to  extreme  alteration,  both 
with  regard  to  the  ftate  of  its  blood-veffels,  and 
L  4  alfo 


i<58  OF  CONCEPTION 

alfo  with  rcfpeft  to  that  of  its  parenchymatous 
portion,  throughout  which  thofe  veilcls  are  inter- 
woven. 

On  the  prefent  occifion  it  may  not  be  impro- 
per to  observe,  that  in  proportion  as  the  impreg- 
nate ]•  uterus  advances  in  magnitude,  its  blood- 
veffe  s  i  i  at  mazy  and  convoluted  appearance, 
for  which  they  are  ar other  times  fo  very  remark- 
able, and  affume  courfes  much  more  rectilineal  or 
dire  ft  ;  while  at  the  fame  time  they  are  fubjefted 
to  a  confi derable  extenfion  of  their  diameters,  and 
a  confequent  increafe  of  their  real  capacities. 
Thus,  even  the  uterine  Teins  have  become  {o  ex- 
tremely capacious  and  prominent,  as  to  har?  been 
piiftaken  by  numerous  anatomifts  for  true  finufes. 

With  regard  to  the  parenchymatous  portion  of 
the  impregnated  uterus,  it  becomes  gradually 
mere  and  more  lax  and  fpongy,  efpecially  where 
it  is  in  contaft  with  the  ovum  contained  ;  fo  that 
towards  its  fundus  or  bottom  it  becomes  confider- 
ably  thick,  and  in  a  living  and  healthy  female,  is 
greatly  diftended  with  blood,  and  poifeiles  the 
powers  of  life  in  a  very  high  degree.  This  or- 
gan is, 'notwithstanding,  (oft  at  the  fame  time, 
and  very  widely  di.Terent  in  its  general  habit  and 
appearance  from  the  firm  and  compact  flefh  of  the 

uterus 


AND  PREGNANCY.  i69 

uterus  in  ^n  uoi  tpregnated  ffcate:  this  difference 
is  ftill  ro  r,i  '•  king  if  the  fubjcfi  containing  t!  e 
gravid  uterus  be  dead,  in  which  cafe,  provided 
pregnancy  be  coi.fiderably  advanced,  this  organ 
falfcJy  aflupies  in  its  texture  (as  was  formerly  well 
obferved  by  Arantius),  a  lamellated  appearance. 

It  may  not  be  amifs,  on  the  prcfent  occafion, 
briefly  to  enumerate  a  few  more  of  the  moil 
imporrant  changes  to  which  the  gravid  uteru  is 
jfubje&ed,  to  ether  with  the  moll  remaikable  i  v.ci 
that  occur  in  the  ovum  and  foetus.  Thefe  changes 
we  will  confider  in  the  fucceffive  order  in  which 
they  appear  throughout  the  feries  of  ten  lunar 
months,  which  period  of  time  is  now,  with  fuffi- 
cient  propriety,  fuppofed  to  conftitute  the  moil 
natural  term  of  pregnancy. 

§  583- 

As  we  uniformly  obferve  the  uterus  beginning 
to  fwell  fhortly  after  the  time  of  impregnations 
(§  567-)  fo  being  from  that  period  incre.ifed  both 
in  bulk  and  weight,  it  defcends  a  little  deeper  into 
the  fnperior  part  of  the  vagina;  notwithstanding 
this  defcent  it  Mill  retains  its  former  figure  in  all, 
except  the  following,  refpe&s,  viz.  its  fundus 
becomes  a  little  more  convex,  its  anterior  paries 
or  wall,  recedes  a  little  farther  from  the  pojlcrior, 
and  its  cavity,  which  was  before  very  narrow  and 

aim  oft 


i-jo  OF  CONCEPTION 

almofl:  triangular,  now  accommodates  itfelf  to  the 
globofe  figure  of  the  ovulum  it  enclofes. 

About  the  end  of  the  firft  month,  the  ovulum 
itfelf  amounts  to  the  fize  of  a  pigeon's  egg,  and 
has  the  two  defciduae  feparated  from  each  other, 
and  alfo  the  fraall  amnion  fituated  at  a  diftance 
from  the  larger  chorion:  about  the  termination  of 
the  third  month  it  attains  the  fize  of  a  goofe's 
egg,  the  caduca  reflexa  becomes  approximated  to 
the  crafla,  and  the  amnion  approaches  nearer  to 
the  chorion.  The  amnion  abounds,  at  this  time, 
with  a  profufe  volume  of  fluid  denominated  liquor 
amnii.  In  this  liquor  the  embryo,  as  yet  very 
tender,  and  extremely  fmall  in  proportion  to  the 
quantity  of  the  furrounding  fluid  (being  at  this 
time  fcarcely  equal  in  magnitude  to  a  fmall  moufe) 
appears  to  iiu&uate  in  a  loofe  and  unfteady 
manner,  and  is  even  now  in  a  precipitate  pofition. 

§  584- 

About  the  fourth  month  after  conception,  the 
uterus  begins  to  aiTume  more  of  an  oval  or  fome- 
what  globe-like  appearance;  its  neck  being  more 
and  more  foftencd,  gradually  fhortened,  and  as  it 
were,  deftroyed,  or  rather  latterly  diftended,  it 
again  protrudes  upwards,  and  begins  to  afcend 
from  the  fmaller  into  the  larger  pelvis.  At  the 
fame  time  the  fallopian  tubes  themfelves,  with  the 

convex 


AND  PREGNANCY.  171 

convex  bottom  of  the  uterus  being  elevated  or 
borne  upwards,  are  thus  extended  and  elongated; 
thefe  tubes  are,  however,  attached  and  connected 
fo  clofely  to  the  fides  of  the  uterus,  that  they 
cannot  recede  from  them,  more  than  one  half  of 
their  own  length;  hence,  when  only  viewed 
fuperficially,  they  appear  to  originate  and  proceed 
from  the  middle  of  the  uterus,  which  has  given 
birth  to  a  very  erroneous  opinion  refpecling  the 
aftonifhing  increafe  of  the  fundus  uteri. 

From  this  time  alfo  the  foetus  acquires  by 
degrees  fuch  an  increafed  magnitude,  as  renders 
it  more  proportionate  to  the  capacity  of  the  ovum, 
and  begins  about  the  fame  period  to  fix  itfelf  in  a 
more  fteady  and  firm  pofition,  which  it  preferves 
till  the  very  clofe  of  parturition  :  in  this  pofition 
its  head  is  placed  in  a  downward  direction,  and 
and  its  face  turned  towards  the  lumbar  region  of 
the  mother,  inclining,  for  the  mod  part,  fo  me  what 
obliquely  towards  the  left  fide. 

§  s#- 

In  the  middle  ftage  of  pregnancy,  which  occurs 
about  the  end  of  the  fifth  month,  the  uterus  has 
attained  fuch  a  magnitude,  that  its  fundus  is 
elevated  to  a  point  half-way  between  the  pubes 
and  umbilicus,  and  the  pregnant  (late  becomes  now 

obfervable 


172  OF  CONCEPTION 

obfervable  from  the  external  appearance  of  the 
abdomen. 


About  lite  fame  time,  the  fceius  becomes  more 
perceptible  to  the  mother  from  the  agitative  mo- 
tion of  its  body,  though  we  are  not  able  to  deter- 
mine, with  accuracy  and  dtfmitude  the  preciie 
period  of  time  at  which  this  motion  takes  place. 
It  appears  now,  however,  to  be  more  vigorous 
and  aclive,  fo  that,  according  to  the  common  ufe 
and  acceptation  of  fpeech,  it  may  be  faid  to  be 
the  unequivocal  action  of  life. 

§  586. 

Throughout  the  five  remaining  lunar  months 
the  uterus,  with  the  foetus  which  it  contains,  make 
gradually  dill  farther  advancements  in  point  of 
magnitude.  Thus,  at  the  end  of  the  fixth  month 
they  reach  nearly  to  the  umbilicus  or  navel ;  and 
about  the  termination  of  the  eighth  approach 
even  the  fcrobiculus  cordis,  in  confequence  of 
farther  protrufion  upwards.  The  cervix  uteri  is 
in  the  mean  time  more  and  more  obliterated,  re- 
duced nearer  to  a  level  with  the  adjacent  parts  of 
that  organ,  and  its  parietes  or  walls  confiderably 
diminhh  in  thicknefs. 

§587- 


AND  PREGNANCY.  173 

§   587- 

Finally,  about  the  end  of  the  tenth  month  after 
conception,  the  uterus  being  opprefTed  and  over- 
powered as  it  were,  by  its  own  bulk  and  weight, 
(its  longitudinal  axis,  amounting  in  general  to  n, 
and  its  tranfverfe  to  9  inches  in  length)  begins 
again  to  fubfide,  and  as  the  period  of  parturition 
approaches,  its  oftium  or  mouth  is  gradually  ex- 
panded, and  thus  exhibits  an  orbicular  or  ring-like 
opening. 

Each  membrana  caduca,  more  efpecially  the 
reflected  one,  which  adheres  to  the  chorion, 
having  been  gradually  attenuated  for  feveral 
months  immediately  preceding,  exhibits  now  a 
kind  of  net-like  appearance  diftinetly  marked  by 
fliort  fibres  of  a  whitiih  colour. 

Such  is  the  fize  of  the  placenta  at  this  advanced 
period,  that  its  greatfefl:  diameter  or  breadth 
amounts  to  about  9  inches,  its  lead  diameter  or 
thicknef;  to  about  one  inch  ;  and  its  weight  10 
about  one  pound,  and  fometimes  more. 

The  length  of  the  umbilical  cord  for  the  moil 
part  equals,  and  fometimes  even  exceeds,  eighteen 
inches. 

The 


i74         OF  THE  NISUS  FORMATIVUS. 

The  weight  of  a  mature  and  wejl  grown  fcetus 
is  nearly  feven  pounds,  its  length  about  twenty- 
inches. 

The  quantity  of  the  liquor  amnii  is  fo  extremely 
variable,  that  it  cannot  poffibly  be  ascertained 
with  any  degree  of  definitude  ;  in  general,  how- 
ever, it  fcarcely  amounts  to  a  pound,  provided  the 
fcetus  be  healthy  and  robuft. 


SECT.    XLV. 

OF  THE  NISUS  FORM  ATI  VUS. 

§  588- 


AVING  thus  enumerated  and  de- 
fcribed,  in  a  plain  and  fimple  manner,  the  mofl 
obvious  and  unequivocal  phenomena  of  concep- 
tions, together  with  fuch  changes  as  are  difcovered 
by  attentive  obfervation  to  fucceed  each  other, 
during  the  progrefiive  courfe  of  pregnancy,  not 
only  in  the  human  ovum  itfelf,  but  alfo  in  the 
fcetus  which  it  embraces,  and  contains,  we  now 
proceed  to  an  inveftigation  of  thofe  phyfical  pow- 
ers, by  the  influence  and  efficacy  of  which  the 

fublime 


OF  THE  NISUS  FORMATIVUS.  17c 

fublime  and  truly  aftonifhing  procefs  of  generation 
appears  to  be  mod  probably  accomplifhed. 

§  589- 

There  are  not  wanting  certain  characters  of 
high  celebrity  and  diftinclion  who  attempt,  even 
in  our  own  times,  to  explain  the  divine  procefs,  in 
the  following  brief  and  fummary  manner ;  they 
contend  that  the  genuine  work  of  actual  generation 
has  not,  at  the  prcfent  time,  any  real  exigence  at 
all ;  on  the  contrary,  they  allege,  that  the  whole 
human  race  pofTeffed,  under  the  form  of  original 
germs,  a  joint  pre-exftence  in  the  genital  fydem  of 
one  or  other  of  our  iirlt  parents,  and  that  thefe 
germs  have  ever  been,  and  are  yet,  fubjecled  to 
gradual  evolutions,  according  as  the  progreflive 
lapfe  of  time,  aided  by  the  co-operation  of  fpecific 
caufes,  has  contributed  to  awaken  them  to  the 
enjoyment  of  open  and  actual  life. 

Unfortunately,  however,  for  «the  advocates  of 
the  foregoing  hypothefis,  an  effential  difference 
of  opinion  prevails  among  them  on  a  point  of 
confiderable  magnitude  and  importance ;  thus, 
while  fome  of  them  are  anxiouily  in  quell  of  thofe 
original  germs  among  the  animalculae  that  peoplr 
the  femen  of  the  male  ;  others  are  fearching  for 
thofe  microfcopic  animals  with  no  lefs  induftry  and 
zeal  in  the  ovaria  of  the  female. 


r7£         CF  THE  NISUS  F0RMATIVU5. 

§  59°- 
To  the  latter  of  thcfe  feels  in  phyfiology,  I  mult 
acknowledge  that  I  myfelf  was  formerly  an  adhe- 
rent.    1   was  lead   to   adopt  the  opinion  of   this 
learned  body  not  only  by  the  refpeetable  autho- 
rity of  its  numerous  advocates,  but  alfo  by  the 
want  of  another  more    rational  and  fatisfattory. 
At  prefect,   however,   I  am  obliged  to  repudiate 
this  do&rine  entirely,  to  confefs  my  errrors,  and 
endeavour   if   poflible    to    correct    them ;  having"- 
been  fully  convinced,  from  a  more  clofe  and  mi- 
nute attention  to  the  phenomena  of  generation, 
that  nature  performs  this  procefs  in  a  manner  quite 
different  from  that  contemplated  and  embraced  in 
the  theory  now  under  confideration. 

§  591- 

For  I   am   indeed   duly   more  and  more  con- 
vinced,  that  all   living   organized  bodies  pofiVfs, 
from  their  earlieft!  effort  at   organization    to  the 
cloiing  glafs  of  their  exiflence,  a  peculiar  power 
perpetually    active,     perpetually    efficacious,    the 
immediate  dedication  of  which  is,  hrit,  to  mould 
the  bodies  in  which  it  refides  into  their  native  and 
Ipecific  forms  by  the  myderious  procefs  of  gene- 
ration, to  preferve  them  afterwards  from  deduc- 
tion by  the  cealelefs  function  of  nutrition,  and,  in 
cafe  of  accidental  mutilation,  to  reftore  their  parrs 
agLiin,  as  far  as  confident  with  the  regular   efta- 
2  bliihments 


OF  THE  NISUS  FORM  ATI  V  US.  177 

blifhments  of  nature,  by  the  procefs  of  repro- 
duction. That  this  energy  may  not  be  confounded 
with  the  other  kinds  of  vital  energy,  let  it  be 
diltinguifhed  by  the  name  of  nifus  formal  ivus. 
By  this  name,  however,  we  mean  to  defignate  not 
fo  much  a  caufe  as  a  perpetual  and  uniform  effect, 
the  exigence  and  reality  of  which  are  deduced 
from  actual  observations  made  on  the  condant  and 
univerfal  occurrence  of  certain  phyfical  pheno- 
mena. It  is  thus,  with  views,  and  on  principles 
entirely  fimilar,  that  we  make  ufe  of  the  terms 
attraction  and  gravitation^  to  denote  certain  ener- 
gies or  fources  of  action,  the  caufes  of  which 
are  notwithstanding  Hill  involved  in  more  than 
Cimmerian  darknefs. 

§  592-  t 

To  me  it  appears,  indeed,  highly  probable,  that 
a  dated  period  of  time  is  requilite  for  accomplish- 
ing the  intimate  mixture,  the  union  and  complete 
concoction  or  maturity  of  thofe  various  inquiline 
humours,  belonging  to  each  frx,  (§  518.  524. 
542.  543.)  which  are  doubtlefs  dif<.  harged  into 
the  cavity  of  the  uterus,  during  every  act  of  fruitful 
coition.  This  term  of  preparation  having  at  length 
elapfed*  and  the  liquors  being  fully  matured  and 
brought  into  the  mod  perfect  (late  of  union  and 
reciprocal  influence,  the  nifus  formativus  is  forth- 
with excited  into  action,  by  means,  of  which  the 

vol.  11.  M  fpercaatic 


i78  OF  THE  NISUS  FORMATTVUS. 

fpermatic  mafs,  hitherto  formlefs  and  chaotic,  fa 
partly  arranged  and  organized  into  the  elegant 
and  beautiful  envelopes  of  the  nafcent  ovulum, 
and  partly  moulded  into  the  figure  of  the  living 
embryo  which  this  minute  bodies  enclofes.  Fron. 
this  theory  we  can  aflign  a  fatisfactory  re;i' 
why  the  uterus,  for  the  two  firft  weeks  after  cc; 
ception,  appears  to  contain  a  mafs  of  crude  and 
fhapelefs  humours  alone,  and  does  not  exhibit, 
even  to  our  bed  glaffes  (now  brought  to  very 
high  perfection),  the  fmalleft  veftige  of  an  or- 
ganized embryo,  which,  notwithstanding  burfts 
into  view  aim  oft  inftantaneoufly  about  the  end  of 
the  third  week,  and  is,  even  on  its  firft  appear- 
ance, of  confiderable  magnitude. 

§  593- 

Of  the  7iif us  format ivus  we  are  prefentcd  with 
more  remote  veftiges  throughout  every  department 
of  natural  bodies,  not  excluding  even  the  moft 
fimple  elements  of  matter,  where  original  germs 
cannot  poflibly  be  fuppofed  to  have  the  fhadow  of 
an  exiftence.  Thus,  the  clouds  themfelves  affume 
their  own  determinate  forms,  and  even  the  ftream- 
ing  torrents  or  veins  of  the  electric  fluid  preferve 
fpecific  figures.  There  are,  again,  in  the  mineral 
kingdom,  fpecimens  of  metallic  chryftallization, 
which,  if  indeed  the  form  alone  be  confidered,  and 

.  .  the 


OF  THE  NISUS  FORMA TIVUS.  179 

the  prerogative  of  life  kept  entirely  out  of  view, 
bear  the  mod  ftriking  refemblance  to  truly  orga- 
nized bodies. 

In  teftimony  of  the  truth  of  this,  we  need  only 
mention  the  curious  hypniform  cryftals  into  which 
refined  or  depurated  copper  fhoots  when  firft 
reduced  to  a  ftate  of  fufion,  or  that  exquifitely 
beautiful  fpecimen  of  native  peruvian  filver  which 
they  call  filicinum  or  fern-like,  from  the  refem- 
blance of  its  figure  to  that  of  the  plant  denomi- 
nated fern. 

§   594* 

In  like  manner  both  the  animal  and  vegetable 
kingdoms  afford  numerous  examples  of  organized 
bodies,  in  which,  from  their  magnitude  being  fuf- 
ficient  to  render  them  vifible,  from  their  beautiful 
and  unclouded  tranfparency  and  from  the  extreme 
rapidity  of  their  progreflive  growth,  the  whole 
procefs  of  generation  is  completely  unmafked  as  it 
were,  and  may  be  fubjected  to  the  examination  of 
the  naked  eye.  The  refult  of  attentive  and  minute 
obfervations  made  on  this  procefs  Li  fuch  fuhje&s 
as  thefe,  will  be  fivfficient  to  evince,  on  the  autho- 
rity of  the  mod  indubitable  teftimony  that,  at  leaft 
in  thefe  bodies,  no  germs  pre-exift.  In  illuftration 
of  the  above  pofition  it  will  be  fufficient  to  mention 
M  2  from 


i3o  OF  THE  NISUS  FORMATIVUS. 

from  among  the  different  individuals  of  the  vege- 
table kingdom,  the  conferra  fontinaUs.  And  from 
thofe  of  the  animal,  the  hydra  viridis. 

§  595- 
I  mould  far  exceed  the  limits  prefcribed  to  thefe 

inftitutions  were  I  to  attempt  a  minute  and  circum- 
stantial detail  of  the  various  arguments  which,  in 
my  view,  nature  herfelf  furnifhes  to  prove  the 
potent  influence  of  the  nifus  formativus  in  the 
procefs  of  generation.  It  may  be  proper,  how- 
ever, briefly  to  (late  a  few  of  them,  the  force  and 
efficacy  of  which  will  appear  fufficiently  evident 
on  the  flight  eft  examination. 

§  596- 
The  firft  argument  I  fhall  further  propofe  on 

this  fubjeft  is  taken  from  the  hiftory  of  thofe 
curious  and  interefting  fubje&s  of  organized  nature 
denominated  hybrids.  From  a  very  beautiful  and 
celebrated  experiment  it  appears,  that,  if  prolific 
female  hybrids  be  fucceilively  through  feveral 
fenerations  impregnated  by  males  of  any  given 
fpecies  different  from  the  fpecies  of  the  females, 
the  new  offspring  will  gradually  deviate  fo  widely 
from  the  original  form  of  the  mother,  and  make 
fuch  evident  and  effectual  ftrides  towards  that  of 
the  father,  as  to  lofe  at  length  every  veftige  of 
fimilitude  to  the  former,  and  become  finally,  (by  a 

fpecies 


OF  THE  NISUS  FORMATIVUS.         til 

fpecies  of  arbitrary  metamorphofis)  completely 
affimikted  to  the  external  figure  and  appearance 
of  the  latter. 


§  597- 

There  exists  a  phenomenon  or  fa<ft  relative  to 
the  hiflory  and  production  of  monjiers,  (the  truth 
of  which  is  too  well  afcertained  and  eftabllfhed 
to  admit  of  a  doubt),  that  merits  our  attention 
while  on  the  consideration  of  the  prefent  intereil- 
ing  and  intricate  fubjecl.  It  is  a  circumftanee  well 
known  to  naturalifls,  that  thofe  animal  produc- 
tions denominated  monjlers  (moft  of  which  are 
fuppofed,  by  the  advocates  for  the  celebrated 
doctrine  of  evolution,  to  have  pre-exifted  in  a 
monftrous  germiform  date  from  their  original  crea- 
tion)— it  is,  I  fay,  well  known,  that  fuch  preter- 
natural productions,  though  very  frequent  among 
certain  fpecies  of  animals  in  a  fubjugated  or  do- 
mestic flare  (more  efpecially  among  fwine),  are 
notwiihfhnding  very  rarely  found  among  the  ori- 
ginal and  free-born  animals  of  the  very  fame  fpe- 
cies, that  have  never  been  reduced  to  an  humble 
ftate  of  domeftication,  but  ftill  range  the  com- 
mons and  wilds  of  nature,  wholly  exempt  from 
the  tyrannic  controul  of  man. 


M  3  §  59S. 


i8z      of  the  nisus  formativus. 

§  598- 

It  is  neceffary  further  to  obferve,  that  not  only 
monftrofities  co-eval  with  the  birth  of  animals, 
but  alfo  fubfequent  adventitious  mutilations  and 
other  /pedes  of  deformity,  whether  produced  on 
the  animal  fyftem  by  accident  or  defign,  become 
now  and  then  completely  hereditary ;  and  thus, 
what  was  at  firft  the  effect  of  art  alone,  may  be 
faid  to  become  at  length  the  actual  work  of  nature 
herfelf. 

§  599* 

The  phenomena  of  re-produftion  in  general  are 
much  more  eafily  and  rationally  accounted  for,  by 
confidering  them  as  the  refult  of  a  nifus  forma- 
tivus, than  by  referring  them  to  the  pre-exiftence 
of  partial  or  .local  germs.  This  obfervation  is 
more  fully  and  clearly  illuflrated,  and  its  truth 
more  forcibly  exhibited  by  an  application  of  it  to 
fome  particular  inftances  of  re-production,  as  that 
of  the  nails,  for  example,  which  after  the  entire 
lofs  of  the  Jir/t,  are  well  known  to  be  frequently 
regenerated  on  the  fecond  phalanx  of  the  fingers. 

§  600. 
Again,  in  certain  parts  of  the  body  where  no 
pre-exiftence  of  germs  can  poflibly  be  fufpected, 
wt  not  unfreqnently  fee  organic  parts  of  a  pre- 
ternatural 


OF  THE  NISUS  FORM  ATI  VU&  183 

ternatural  order  produced  by  rhe  wis  medicatrix 
natures,  when  roufed  into  action  in  confequencc 
of  accidental  difeafes  :  As  an  example,  and  in 
illuftration  of  this,  we  may  mention  thofe  fmall 
ofiifications  known  by  the  name  of  ojficula  Wor~ 
miana,  which,  in  cafes  of  hydrocephalus  internusy 
are  formed  by  the  provident  powers  of  the  ani- 
mal fyftem,  for  the  purpofe  of  arching  over  and 
thus  completely  clofmg  the  enlarged  fontanel. 

Finally,  on  comparing  with  candour,  and  weigh- 
ing with  impartiality,  the  various  arguments  on 
each  fide  of  the  queftion,  it  very  evidently  ap- 
pears, that  befides  a  power  of  exciting  to  motion 
and  action,  which  the  advocates  for  the  pfe-ex- 
iftence  of  germs  attribute  to  the  male  femen,  in 
order  to  render  their  favourite  theory  more  fpc- 
cious  and  plaufible,  they  mud  alio  beftow  on  that 
fluid  plajlic  or  formative  powers  of  the  utmoft 
extent  and  influence :  Whence  it  is  obvious,  that 
the  do&rine  for  which  they  fo  zealoully  contend, 
is  of  itfelf  wholly  inadequate  to  the  explanation 
of  the  numerous  and  intricate  phenomena  of  ge- 
neration, unlefs  it  be  aided  by  the  powerful  con- 
currence of  a  nifus  formativus:  Whereas,  en  the 
other  hand,  the  fyftem  which  we  have  j nil  pro- 
pofed  on  the  fubjecl  is,  without  the  bold  pre- 
emption of  prc-exijicnt  germs,  fully  fuflicient  to 
explain  all  the  multiplicity  of  phenomena  attend- 
ed 4  ant 


xfi4  OF  PARTURITION. 

ant  on  this  divine  procefe.  Let  us  then  on  the 
prefent,  as  we  fhonld  on  every  other  point  of  ccn- 
troverfy,  adhere  to  that  doctrine  which  is  raoft 
fimple  in  its  nature,  and  mod  condufive  in  its  end, 
from  a  thorough  conviction,  that  an  unneceffary 
multiplication  of  entities  or  caufes  is  no  lefs  repug- 
nant to  real  and  practical  utility,  than  to  the  tenor 
and  fpirit  of  found  philofophy. 


SECT.    XLVI. 

OF  PARTURITION,    AND  ITS  CONSEQUENCES. 
§    602> 

JL  HE  foetus  being  regularly  formed  and 
faihioned  by  the  energies  of  which  we  have  hi- 
therto treated,  and  advanced  through  the  pro- 
greffive  ftages  of  its  fubfequent  growth,  till  it  be 
brought  to  a  ftate  of  fcetal  perfection,  rauft,  after 
arriving  at  this  particular  period  of  maturity,  be 
finally  ufhered  into  the  enjoyment  of  light  and  en- 
tire life,  by  the  painful  bufinefs  of  parturition. 

§    603. 
This  critical  and  important  period  arrives,  agree- 
ably to  the  ufual  order  of  fpontaneous  nature, 
(which  is  the  only  object  contemplated  in  phyfio- 


OF  PARTURITION.  185 

logy),  about  the  termination  of  the  tenth  lunar 
month,  i.  e.  about  the  39th  or  40th  week  after 
conception. 

§  604. 
When  a  pregnant  female  finally  arrives  at  this 
eventful  crifis,  Ihe  is  forcibly  impelled  to  the  la- 
bour of  parturition  by  an  infuperable  neceffity, 
already  faid  (§  295.)  to  be  lefs  fubjett  to  the  con- 
troul  of  the  will  than  that  which  urges  to  the  per- 
formance of  any  other  function  belonging  to  the 
human  body. 

§   605, 

With  refpeft  to  the  caufes  of  a  revolution  fo 
determinate  and  hidden,  different  and  even  oppo- 
fite  opinions  have  been  entertained  by  different 
phyfiologifts.  When  we  view,  and  take  into  at- 
tentive confideration,  all  the  attendant  circum- 
ftances,  it  appears  neceffary  to  refer  the  caufe, 
which  immediately  impels  to  parturition,  to  an 
eternal  law  of  nature,  which  has  hitherto  received 
no  better  explanation  than  has  been  given  to  a 
great  many  other  phyfical  phenomena,  which  take 
place  in  like  manner  at  regular  and  Jlated  periods ; 
fuch,  for  example,  as  the  metamorphofis  of  infers, 
the  progreffive  ftages  of  eruptive  fevers,  their 
crifes,  &c.  &c  .Without  fubje&ing  themfelves  to 
the  juft  charge  of  fancifully  entering  on  an  abfurd 

fpeculation, 


1 86  OF  PARTURITION. 

fpeculation,  certain  phyfiologifts  have  compared  a 
mature  ovum,  in  the  uterus  of  the  human  fubjeft, 
to  the  healthy  fruit  of  vegetables,  which  when 
completely  ripened,  fall  fpontaneoufly  from  their 
parent  plants,  in  confequence  of  a  felf-conjlriclion 
of  the  vdTels  through  which  rheir  nourilhment 
was  conveyed.  It  has  been  in  like  manner  ob- 
ferved,  that  as  the  period  of  parturition  ap- 
proaches, the  human  placenta  fuffers  a  flight  de- 
gree of  conftri&ion,  and  becomes  thus  prepared, 
as  it  were,  for  its  impending  reparation  from  the 
furrounding  uterus. 

With  regard  to  the  opinion  entertained  on  this 
fubjecT  by  phyfiologifts  in  general,  namely,  that 
the  amazing  expanfion  to  which  the  impregnated 
uterus  is  fubje&ed,  with  a  multitude  of  other  im- 
preffions  or  impulfive  powers  of  a  like  nature,  acT 
as  the  genuine  exciting  caufes  of  parturition,  it 
appears  to  be  very  clearly  and  effectually  invali- 
dated by  a  great  variety  of  arguments,  which  may 
be  fairly  deduced  from  the  unequivocal  pheno- 
mena of  the  animal  economy  itfelf :  of  thefe  argu- 
ments we  think  proper  to  mention  the  following, 
namely,  in  numberlefs  genuine  cafes  of  extra- 
uterine conception,  where  the  fcetufes  have  been 
contained,  for  example,  in  the  Fallopian  tubes,  or 
in  the  ovaria,  the  uterus  has  notwithftanding  been 
attacked  by  painful  and  convulfive  throws,  about 

the 


OF  PARTURITION.  187 

the  termination  of  the  tenth  lunar  month  after  the 
occurrence  of  fuch  preternatural  conception. 

§  606. 

Befides  the  exciting,  it  is  evident  that  there 
mufl  be  alfo  the  joint  co-operation  of  very  pow- 
erful efficient  caufes,  arifing  from  the  nature  and 
properties  of  the  uterus  itfelf,  and  of  the  contents 
which  it  enclofes. 

The  proximate  or  immediate  and  primary  caufe 
mufl  be  doubtlefs  referred  folely  to  the  vita  pro- 
pria,  or  fpecific  life  of  the  uterus  itfelf  (§  47.) 

Of  the  remote  caufes  the  leading  and  moft  con- 
fiderable  appear  to  be,  the  powerful  efforts  which 
are  made  by  the  afMance  of  the  procefs  of  refpi- 
ration,  and  the  extenfive  confent  or  co-operation 
of  the  intercoflal  nerve  with  the  other  portions 
of  the  nervous  fyftem. 

§  607. 
"When  finally  the  labour  of  genuine  parturition 
is  excited,  its  phenomena  obferve  a  determinate 
and  regular  order  with  regard  to  their  commence- 
ment and  fubfequent  progreffive  courfe.  In  con- 
fequence  of  this,  they  have  been  divided  by  ac- 
coucheurs into  different  Jiages,  of  which  four 
have  been  enumerated  by  the  lateft  writers  on  the 
pbfletric  art. 

§  608. 


i88  OF  PARTURITION. 

§    608. 

In  the  jirft  ftage,  the  parturient  patient  expe- 
riences a  flight  attack  of  thofe  peculiar  and  well- 
known  pains,  called  in  that  (late  prccurfors  01 
ivarnings,  which  (hoot  in  a  direction  from  the 
loin?  to  the  lower  parts  of  the  uterus,  and  which 
are  indeed  felt  at  intervals,  (though  with  dimi- 
nifhed  frequency  and  force),  throughout  the  whole 
period  of  parturition  :  the  orifice  of  the  uterus 
begins,  at  the  fame  time,  to  be  confiderably  di- 
lated, the  abdominal  tumor  fubf  des,  an  inciina- 
tion  to  pafs  urine  becomes  urgent  and  trouble- 
fome,  and  a  copious  difcharge  of  mucus  takes 
place  from  the  genital  organs,  now  in  a  Hate  of 
diflenfion  and  laxity. 

§  609. 
In  the  fecond  ftage,  the  pains  increafe,  and  are 
now  diflinguifhed  by  the  name  of  preparantes,  or 
preparatory  efforts  :  the  inferior  fegment  of  the 
coverings  or  membranes  of  the  ovum  are,  at  the 
fame  time,  protruded  through  the  uterine  orifice 
into  the  vagina. 

§    610. 

In  the  third  ftage  the  pains  Mill  continue  greatly 
augmented  in  their  violence,  and  are  now  denomi- 
nated dolor -es  ad  par  turn  *.     They  aft  againft  the 

*  i.  e.  The  genuine  pains  of  parturition. 

uterus 


OF  PARTURITION.  189 

uterus  with  a  more  violent  impetus,  and  thus 
potently  protrude  it  downwards,  while,  ar  the  fame 
time  the  uterus  prefTes  with  fuch  aftonifliing  force 
on  the  encarcerated  foetus,  as  to  occafion  a  rup- 
ture in  the  membranes  by  which  it  is  inclofed. 

§  6n. 

During  the  fourth  and  laft  flage  of  parturition, 
while  the  patient  i  ited  vvith  convulfive  throws, 

and  tortured  with  the  mod  excruciating  pain,  (lie 
makes,  at  length,  a  violent  exertion,  (not  un- 
frequently  accompanied  with  horripilation,  grind- 
ing of  the  teeth,  trembling  of  the  knees,  &o),  by 
the  impuifive  force  of  which,  the  head  of  the 
emerging  iniant  is  urged  forward,  and  finally  pro- 
truded quite  through  the  external  orifice  with  its 
face  foremoft :  in  this  unlooked  for  pofition  it  is 
forced  to  advance,  in  confequence  of  the  vertex 
or  crown  of  the  head  becoming  lodged  againft  the 
arch  of  the  pubes,  while  its  other  parts  are  urged 
onward,  and  obliged  to  revolve  on  the  flationary 
vertex,  as  on  an  axis,  or  centre  of  motion.  Thus, 
amidft  a  profufe  difcharge  of  blood,  the  infant  is 
finally  excluded  from  its  place  of  confinement,  and 
introduced  to  the  enjoyment  of  light  and  life. 

§   612. 

The   foetus  being   thus  happily  excluded,  the 
birth  of  the  fecundines  fuxceeds,  after  a  fhort  in- 
terval, 


9»  OF  PARTURITION. 

terval,  accompanied,  in  like  manner,  with  painful, 
though  much  lefs  violent,  throws  :  this  latter  birth 
is,  as  well  as  the  former,  followed  by  a  difcharge 
of  blood,  from  that  part  of  the  uterine  cavity  to 
which  the  placenta  adheres  by  means  of  the 
crajfa  or  grofs  membrana  decidua. 

§   613. 

The  uterus,  being  thus,  at  once  delivered  of 
its  two-fold  birth,  by  which  it  had  been  encum- 
bered and  oppreffed,  is  now  contracted  by  little 
and  little,  till  it  is  finally  reftored  to  its  former 
figure,  and  reduced  almoft  to  its  former  fize. 

§   614. 

During  the  firft  week  after  the  birth  of  the 
child,  there  exifls,  from  the  genital  organs  of  the 
mother,  an  uninterrupted  eifufion  of  the  lochia, 
a  difcharge  very  much  refembling  the  catamenia, 
except  that  it  is  more  profufe  in  quantity,  efpe- 
cially  when  not  in  any  meafure  checked  or  dimi- 
nifhed,  by  the  commencement  of  laflation.  The 
bloody  or  florid  colour  of  the  liquid  difcharged  by 
this  evacuation  is,  notwithstanding,  changed  about 
the  fourth  day  to  a  pale  red,  and  from  thence 
pafles  on  to  afTume  a  white  appearance. 

As  foon  as  the  uterus  is  thoroughly  cleanfed 
of  all  remaining  fragments  of  its  deciduous  mem- 
brane, 


OF  THE  HUMAN  SUBJECT,  &c.         191 

brane,  and  has  thus  finally  completed  the  painful 
and  tedious  tafk  of  propagation,  it  may  again 
refume  the  natural  procefs  of  mcnJiruaUon^  or 
even  return  to  the  performance  of  frefh  immola- 
tions on  the  altar  of  conception  itfelf. 


SECT.     XLVIII. 

OF  THE  DIFFERENCES  BY  WHICH  THE  HUMAN 
SUBJECT  IS  CHARACTERISED  BEFORE  AND  AFTER 
BIRTH. 

§    615. 

Jf  ROM  what  has  been  already  faid 
refpe&ing  the  mode  of  life  enjoyed  by  the  fcetus, 
while  yet  encarcerated  within  the  parietes,  and 
immerfed  in  the  warm-bath  of  the  maternal  uterus, 
it  is  extremely  obvious  that  an  immenfe  difference 
mud  exift,  between  the  functions  of  the  animal 
economy  in  this  (late,  and  that  which  Ihortly  fuc- 
ceeds,  when  the  infant  is  finally  introduced,  by 
birth,  into  entire  life,  and  is  poffeffed  of  a  power 
of  fpontaneous  motion.  An  enumeration  and 
ftatement  of  the  leading  points  or  circumftances 
of  this  difference,  conftitutes  the  defign  of  the 
prefent  fe&ion. 

S  616. 


i5;2  OF  THE  HUMAN  SUBJECT 

§  616. 
To  begin  then  with  the  circulation  of  the  blood, 
it  mud  be  obferved,  that  the  route  of  this  crimfon 
fluid  is  different  in  the  festal  dare,  from  what  it  is 
in  that  which  immediately  fucceeds  paturition  or 
birth.  During  the  continuance  of  the  former 
ftate,  the  fcetus  is  connected,  and  preferves  a  cir- 
cular intercourfe  with  the  uterine  placenta,  by 
means  of  the  umbilical  cord  ;  it  has  never,  as  yet, 
infpired  air  for  the  purpofe  of  fupplying  the  blood 
with  that  vital  pabulum,  a  procefs  which  immedi- 
ately commences  and  is  uniformly  continued  after 
birth,  when  this  reciprocal  connection  between 
the  mother  and  child,  is  finally  deftroyed. 

§  6*7. 

The  umbilical  vein  originating  from  the  placenta 
of  the  mother,  and  paffing  through  what  is  called 
the  umbilical  ring  of  the  fcetus,  directs  its  courfe 
towards  the  liver,  where  it  difcharges  its  blood 
into  the  fmus  of  the  vena  portarum  ;  from  thence 
the  blood  is  diftributed  in  part,  by  the  ramifica- 
tions of  this  memorable  vein,  throughout  the  liver, 
and  in  part,  conveyed  by  a  direct  route  through 
the  ducltis  venofus  Arantii,  to  the  inferior  or 
afcending  vena  cava. 

The  two  foregoing  canals,  namely,  both  that 

portion  of  the  umbilical  cord  which  is  contained 

1  in 


BEFORE  AND  AFTER  BIRTH.  193 

in  the  abdomen  of  the  foetus,  and  alfo  the  ductus 
venofus  mentioned  above,  fuller  after  birth  an 
entire  obliteration  of  their  cavities,  and  afTumethe 
nature  and  appearance  of  folid  cords,  jnfomuch 
that  the  former  conftitutes  what  is  denominated 
the  round  lhament  of  the  liver. 


a 


§  618. 

When,  in  the  foetus,  the  blood  is  conveyed 
from  the  inferior  vena  cava  to  the  right  fide  of  the 
heart,  the  greater  part  of  it  is  denied  a  paffage 
from  thence  through  the  lungs,  and  is  therefore 
directed  towards  the  left  or  pofterior  auricle  of 
the  heart,  by  the  valve  of  Euftachius,  and  admit- 
'ted  into  that  cavity  through  the  foramen  ovale* 

§   619. 

For  over  the  mouth  of  the  inferior  vena  cava, 
after  its  afcent  from  the  cavity  of  the  abdomen  in 
the  foetal  (late, a  valve  of  alunated  figure  is  extended, 
which,  in  honour  of  its  immortal  difcoverer,  has 
been  called  the  valve  of  Euftachius.  This  luni- 
form  body  is,  for  the  mod  part,  gradually  oblite- 
rated as  life  advances,  although  in  the  fcetal  (late  it 
appears  to  perforin  the  important  office  of  directing 
the  blood,  emerging  from  the  abdominal  cavity, 
towards  an  orifice  to  be  fpoken  of  prefently,  which 
penetrates  the  feptum  fituated  between  the  two 
auricles  of  the  heart. 

vol.  u.  N  §  620. 


i£4  OF  THE  HUMAN  SUBJECT 

§  620. 
The  orifice  referred  to  in  the  preceding  para- 
graph is  called  the  foramen  ovale,  through  which 
by  far  the  greater  part  of  the  afcending  column  of 
blood,  derived  immediately  from  the  inferior  vena 
cava,  is  conducted  into  the  left  auris  of  the  heart 
during  each  diaftole  of  the  auricles :  of  this  blood 
the  regurgitation  is  effectually  prevented,  by  the 
elegant  falciform  valve  formerly  mentioned,  which 
is  clofely  fpread  over  the  foramen,  and  appears  to 
clofe  that  orifice  completely,  during  each  fyftolic 
motion  of  the  auricles.  During  the  firfl:  years  of 
infancy  the  foramen  ovale  is  in  part  clofed  by  means 
of  this  frnall  valve,  and  partly  obliterated  by  the# 
gradual  but  flow  adhefion  of  its  fides :  in  cor- 
refpondence  to  fuch  adhefion,  the  valve  of  Eufta- 
chius  itfelf  undergoes  alfo  a  flow  and  gradual 
diminution  in  point  of  fize,  till  fcarcely  a  wreck  of 
it  is  left  behind. 

§    621. 

Of  that  blood  which,  at  the  fame  time,  enters 
the  right  auricle  of  the  heart  from  the  fuperior 
vena  cava,  a  veryfmall  portion  only  can  be  received 
by  the  lungs  of  the  lcetus,  as  yet  in  a  weak  and  in- 
active condition  :  it  is  therefore  taken  up  by  the 
duclus  arteribfus,  from  the  trunk  of  the  pulmonary 
aitery  (of  which  this  duct  is  indeed  the  leading 
branch)  and  conveyed  by  a  direct  and  fpeedy  route 

to 


BEFORE  AND  AFTER  BIRTH.  i$$ 

to  the  arch  of  the  aorta,  without  paffing  through 
the  lungs  at  all.  Within  the  courfe  of  a  few  weeks 
after  the  birth  of  the  infant,  the  cavity  of  the 
du&us  arteriofus  is,  for  the  moft  part  obliterated, 
and  its  parietes  or  walls  converted  into  the  nature 
and  appearance  of  a  denfe  and  firm  ligament. 

§  622. 
The  blood  being  propelled  through  the  trunk 
of  the  aorta,  that  portion  of  it,  deftined  to  be 
re-conveyed  to  the  fyftem  of  the  mother,  enters 
the  umbilical  arteries  (§  5^8.)  which  pafs  through 
the  annulus  wnbilicalis,  on  each  fide  of  the  urachus^ 
and  are,  in  like  manner,  after  the  birth  of  the 
infant,  converted  into  folid  imperforated  cords. 

§  623. 
As  the  lungs  perform  in  the  fcetus  fcarcely  any 
fun&ion  at  all,  their  general  habit  and  appearance 
differ  very  materially  from  thofe  which  they  aflume 
after  the  infant  has  commenced  the  procefs  of 
refpiration.  Thus,  their  bulk  is  proportionably 
much  lefs,  their  colour  more  dark,  their  fubftance 
more  compact,  and  hence  their  fpecific  gravity  (o 
much  greater,  that  when  immerfed,  recent  and 
free  from  putrefaction,  into  a  vefTel  of  water,  they 
fink  inftantly  to  the  bottom ;  whereas,  on  the 
other  hand,  if  the  infant  has  been  born  in  a  living 
Itate,  and  taken  in  air  by  infpiration,  thcfe  vifcera, 
N  2  '  tlic 


OF  THE  HUMAN  SUBJECT 

for  the  mod  parr,  float  on  the  furface  of  water,  or 
of  any  ether  fluid  equally  ponderous.  The  right 
lobe  of  the  lungs  appears  to  polTefs  the  peculiar 
prerogative  of  being  dilated  a  little  fooner  than 
the,  left  by  the  incipient  influx  of  air  in  the  fir(t  act 
of  infpiration.  With  regard  to  the  other  pheno- 
mena of  this  new  function  of  life,  they  were 
enumerated  formerly,  when  we  were  treating 
particularly  or  the  procefs  of  refpiration. 

§   624. 

From  the  obfervations  which  were  formerly 
propofed  on  the  nutrition  of  the  foetus  (§  574, 
581.),  it  may  be  very  eafily  perceived  that  the 
ftate  and  condition  of  the  alimentary  tube  and  cby- 
lopoietic  fyftem9  are  extremely  different  before, 
from  what  they  are  after,  the  birth  of  the  infant, 
thtfe  vifcera  being  in  the  firft  cafe  inert  and 
wholly  incapable  of  action.  Thus,  for  inflance, 
in  the  render  embryo  of  only  a  very  few  months 
ejeiftence,  the  larger,  are  perfectly  fimilar  in  habit 
and  appearance  to  the  /mailer,  intejlines;  but 
during  the  clofiflg  months  of  pregnancy  the  former 
portion  of  the  inteftinal  canal  (being  confiderably 
#ftended  with  meconium')  appears  to  merit  unequi- 
vocally that  name  by  which  it  is  afterwards  d\{- 
tinguHhed  from  the  latter. 

§   625. 


BEFORE  AND  AFTER  BIRTH.  197 

§    625. 

The  meconium  is  a  peculiar  fpecies  of  faburra, 
of  a  green  colour,  (haded  with  more  or  lefs  of  a 
brownifh  caffc.  It  is  douhtlefs  derived  from  the 
inquiline  humours  of  the  foetus  itfeU,  more  efpe- 
cially  from  the  bile:  that  it  is  indeed  of  a  bilious 
origin  we  are  induced  to  believe  from  the  follow- 
ing  conliderations: — Firji,  becaufe  the  earlicfi 
appearance  of  this  excrementious  fubftance  cocref* 
ponds  exactly,  in  point  of  time,  with  the  com- 
mencement of  the  biliary  fecretion;  and,  Secondly  > 
becaufe  we  learn  from  accurate  obfervation,  that 
ftich  monPters  as  are  deftitute  of  a  liver,  have  their 
inteftines  fupplied  with  nothing  elfe  but  a  final! 
quantity  of  colourlefs  mucus  ioftead  of  the  more 
common  and  natural  meconium. 

§  626. 
In  the  new-born  infant  the  form  of  the  ccccum 
is  a'fo  very  widely  different  from  what  it  is  in  rhe- 
future  periods  of  life;  and  this  inteftine  is  then 
continued  in  a  direct  line  with  the  appendicula 
vermiformis* 

§   627. 
Several  other  differences  and  peculiarities,  of  a 
fnnikir  nature,  we  have  already  fpoken  of  on  parti- 
cular occafions,  and  ihall  here,  therefore,  only 
N  t.  glance 


io8  OF  THE  HITMAN  SUBJECT 

glance  an  them  in  the  moft  brief  and  tranfienj; 
manner : 

They  are  the  Urachus  (§  579.)  the  membrana 
pupillaris  (§  259.)  and,  in  the  male  foetus,  the 
defcent  of  the  tejies  (§  501.) 

A  few  additional  peculiarities  will  be  fpoken  of 
with  more  propriety  in  the  following  fection. 
Others,  as  being  of  lefs  importance,  we  volun- 
tarily pretermit  in  perfect  filence. 

§  628. 
The  prefent  appears  to  be  indeed  a  very  fit 
and  favourable  opportunity  for  calling  the  attention 
of  the  reader  to  three  parts  of  the  human  body, 
altogether  peculiar  in  their  nature  and  obfeure  in 
their  destination,  which  are  of  a  greater  propor- 
tional fize  in  the  fcetus  than  in  the  adult,  and 
appear  to  be  in  a  fpecial  manner  fubfervient  to 
the  economy  of  the  former.  The  true  and  une- 
quivocal ufes  of  the  parts  now  in  contemplation 
have  not  as  yet,  however,  been  clearly  and  fatif- 
fa&orily  afcertained,  although,  anxioufly  fought 
after  by  the  combined  labours  of  numerous  and 
very  refpeclable  anatomifls.  Thefe  parts  ~  are 
designated  by  the  name  of  glands,  although  their 
parenchy?na  is  far,  very  far,  different  from  the 
g'andular,  and  they  have  never  been  difcovered 

to 


BEFORE  AND  AFTER  BIRTH.  199 

to  pofiefs  the  fainted:  veftige  of  an  excretory  duel:. 
They  are  denominated  the  thyroid  glands  the 
thymus,  and  the  rencs  fuccenturiatati. 

§  629. 
The  thyroid  gland  is  fituated  on  the  anterior 
fide  of  a  cartilage  of  the  fame  name,  which  enters 
into  the  conformation  of  the  larynx.  It  confifts 
of  two  lobes,  and  is  of  a  lunated  or  falciform 
figure;  in  the  fcetus  it  is  diftended  with  a  lympha- 
tic fluid,  but,  as  life  advances,  becomes  gradually 
more  and  more  fpoliated  of  its  diftending  liquid. 

§   630. 

The  thymus  confifts  of  a  mafs  of  fhining  and 
very  tender  fle(h,  is,  in  like  manner  with  the  pre- 
ceding fubftance,  bilobular,  now  and  then  divided 
into  two  diftincl:  portions,  and  contains  alfo  occa- 
sionally a  cavity  of  conilderable  dimenfions.  This 
body  is  fituated  beneath  the  middle  and  upper 
part  of  the  fternum,  and  afcends  on  each  fide  even 
to  the  throat  itfelf;  in  the  fcems  it  is  large, 
irregular  in  its  figure,  and  abounds  with  a  juice  of 
a  milk-like  nature;  but  as  youth  advances  it  gra- 
dually diminiihes  in  fize,  until,  finally,  on  the 
acceffion  of  old  age,  it  is  fo  completely  obliterated 
as  to  exhibit  fcarcely  a  fhadow  of  its  former 
exigence. 

N  4  §  631, 


206       0E  THE  INCREASE,  MATURITY, 

§  631. 
Laflly,  The  Irenes  fucccnturlatali^  (called  like- 
wife  glandula  fuprarenalcs^  capful  a  airabiliati<2y 
&c.)  are  fuuated  beneath  the  diaphragm,  reding 
on  the  upper  extremities  of  the  kidneys.  In  adults 
they  are  not  only  diminifhed  in  fize,  but  are  alfo 
removed  to  a  fmall  diflance  from  the  contact  of 
the  kidneys,  and  contain  a  dark  coloured  fluid, 
which  in  the  fcetus  is  more  inclined  to  a  pale  red. 


SECT.    XLVIII. 


OF  THE  INCREASE,  MATURITY,  AND  DECLINE 
OP  MAN. 


§    632. 

JriAVING  hitherto  minutely  confidered 
the  human  economy,  in  detail,  agreeably  to  the 
feveral  claffes  into  which  its  phyfical  functions  arc 
divided,  nothing  further  remains  at  prefent  than 
to  take  a  general,  brief,  and  comprehensive  furvey 
of  man  in  his  tranfit  over  the  diverfifled  fhge  of 
life,  and  thus  accompany  him,  from  his  earlieft 
vital  pulfe  in  an  embriotic  (late,  throughout  the 

leading, 


AND  DECLINE,  OF  MAN.  201 

leading  revolutions  and  eras  in  his  economy,  down 
to  the  final  termination  of  his  exiftence. 

§  633- 
Firji,  then,  about  the  third  week  after  concep- 
tion, the  rudi  menial  organization  of  the  embryo 
appears  to  take  place  f§  S7S')'-  about  tne  fourth 
week  afterwards,  while  the  embryo  flill  enjoys  an 
extremely  low  and  languid  degree  of  life,  border- 
ing even  on  that  of  a  vegetable,  it  is  fupplied  with 
the  frit  portion  of  genuine  red  blood  (§  13.) 
The  motion  of  the  corculum  or  minute  heart,  has 
been  but  very  feldom  obferved  by  pbyfiologifts  in 
the  incipient  human  embryo,  but  was  long  fince 
difcovered  by  Ariftotle  in  the  incubated  chick,  and 
has  been,  from  that  period,  defignated  by  the 
name  of  the  punclu?n  fallens. 

§  634. 

About  the  feventh  or  eighth  week  after  con- 
ception, the  momentous  procefs  of  q/ieogeny,  or 
the  generation  of  bone,  commences  in  the  human 
fubjeft.  Thofe  parts  where  offeous,  or  bony 
matter  makes  the  fird  depofuions  for  the  formation 
of  its  nuclei,  are  the  clavicles,  the  ribs,  the  verte- 
brae, the  long  cylindrical  bones  of  the  extremities, 
the  mandible  or  lower  jaw,  and  certain  other- 
bones  of  the  face,  &c.  Thcfe  parts  again  where 
the  offeous  depoihiens  are  fecondary  in  point  of 

time, 


202       OF  THE  INCREASE,  MATURITY, 

time,  are  fome  of  the  plain  bones  of  the  lkull, 
fuch,  for  example,  as  the  frontal  and  occipital: — 
while  the  bones  of  the  neck,  &:c.  are  formed  at  a 
flill  later  period. 

The  younger  the  embryo  is,  in  particular,  or  to 
proceed  on  a  more  extenfive  and  general  fcale, 
the  younger  the  human  fubjett  is,  whether  before 
or  after  birth,  with  the  greater  rapidity  does  its 
growth  advance,  and  vice  verfa. 

§  635- 

About  the  middle  period  of  pregnancy,  the 
foetus  becomes  what  may  be  called  a  genuine  fub- 
je&  of  vitality  or  life,  agreeably  to  the  rule  of 
difcrimination  laid  down  on  that  particular  point  in 
a  former  part  of  this  work  (§  585.)  About  the 
fame  time,  the  fecretion  of  certain  humours  make 
their  firft  appearance,  fuch,  for  example,  as  the 
fat  (§  38)  and  the  bile. 

§  636. 
As  the  fcetus  advances  towards  maturity  the 
tender  hair  begins  to  pullulate,  the  nails  emerge 
into  view,  the  membrana  pupillaris  gives  way 
(§  260),  and  in  the  male  fex  the  tejles  begin  to 
defcend  (§  505). 

§  637- 


AND  DECLINE,  OF  MAN.  203 

§  637. 
About  the  clofe  of  the  tenth  lunar  month,  the 
infant  is  finally  releafed  from  its  imprifonment  by 
means  of  parturition  (§  603);  after  which,  befides 
the  aftoniihing  revolutions  in  almoft  the  whole 
economy  of  its  fyflem,  detailed  more  amply  and 
minutely  above,  it  is  alfo  fubjected  to  various 
changes  in  its  external  habit  and  appearance; 
thus,  for  inftance,  that  delicate  lanuginous  hair, 
with  which  the  face  of  the  new-born  infant  is 
overfpread,  difappears  by  degrees,  its  wrinkles  are 
gradually  obliterated,  its  anus  retires  within  the 
nates,  which  now  begin  to  be  flowly  protruded, 
&c.  &c.  &c. 

§  638. 

The  infant  alfo  learns,  (though  indeed  by  very 
flow  degrees),  the  exercife  of  the  various  faculties 
of  the  mind,  fuch,  for  example,  as  thofe  of  per- 
ception, of  attention,  of  reminifcence,  of  defiring, 
&c.  &c.  from  whence,  in  a  very  few  months  after 
birth,  it  is  fubjected  to  dreams,  &c. 

§   639. 

The  organs  of  the  external  fenfes  undergo  alfo 
gradual  or  progreffive  improvements,  and  are 
advanced  to  (till  higher  and  higher  degrees  of 
perfection,  fuch  as  the  external  ears,  the  internal 

nares, 


2o4       OF  THE  INCREASE,  MATURITY, 

nares,   alfo   the  coverings   of  the  eyes,  fuch   as 
ihtirfupra- orbital  arches,  their  fnpercilia,  &c. 

§   640. 

The  bones  of  the  cranium  acquire,  in  the  mean 

time,  an   augmented  degree   of  firmnefs.      The 

fonticuli  or  chafms   between  the  different   bones 

are  gradually  arched  over,  and  about  the  eighth 

month  the  procefs  of  dentition  commences. 

§    641. 

The  infant  is  now  ready  to  undergo  abluchition 

or  weaning,   being  furniflied   with  teeth  for  the 

exprefs  purpofe  of  fubduing  more  folic!  food,  and 

not  to  injure  the  papilla,  or  nipple  of  the  mother. 

§  642. 
About   the   clofe   of  the  firft  year,  the  infant 
learns  to  (land  alone,  and  fupport  i'felf  in  an  < 
pofition,  the  greateft  and  mod  enviable  prerogative 
with  which  the  human  body  is  dignified. 

§  643. 
The  infant  being  thus  removed  from  its  mother's 
breail,  and  poflefUng  the  ufe  and  command  of  its 
feet,  makes  daily  advances  in  growth,  and  im- 
proves in  the  power  of  fpontaneous  motion,  while 
it  acquires,  at  the  fame  time,  another  very  import- 
ant privilege  conferred  on  the  human  race,  namely, 
the  ufe  of  fpccch.      Ideas  which   have  become 

familiar 


AND  DECLINE  OF  MAN.  205 

familiar  to  its  mind  it  now  begins  to  make  attempts 
to  exprefs  by  the  aid  of  that  important  organ  the 
tongup* 

§  644. 
About  the  feventh  year  of  life,  the  milk-teeth, 
or  firfl  fet,  being  twenty  in  number,  drop  out  by 
degrees,  and  are  replaced  in  a  feries  of  years  by 
a  fecond  dentition,  confuting  of  thirty-two  peren- 
nial or  permanent  teeth. 

§  645. 
During  this  period  of  infancy  the  memory  far 
furpafies  in  ftrength  and  perfection  the  other  pow- 
ers of  the  mind,  and  appears  to  be  indeed  in  a 
very  peculiar  manner  adapted  for  receiving  and 
retaining  the  figns  of  things ;  whereas  after  the 
fifteenth  year  of  life,  the  glowing  powers  of  the 
imagination  ufually  gain  the  afcendency. 

§   646. 

This  fuperior  ftrength  and  activity  of  the  ima- 
gination very  happily  manifefls  itfclf  throughout 
thofe  years  of  life  in  which  the  human  fubjeft  is, 
by  a  variety  of  (Inking  and  very  important 
changes  in  the  body,  gradually  prepared  for  the 
future  performance  of  fuch  functions  as  conftitute 
the  ciiaracteriftic  diftindtions  between  the  two 
fexes. 

§  647- 


2o<5      OF  THE  INCREASE,  MATURITY, 

§  647. 
Shortly  after  this  period  the  mamma;  or  breads 
of  the  female  fubject  begin  to  fwell,  the  chin  of 
the  male  becomes  clothed  in  a  mantle  of  coarfer 
down,  and  a  variety  of  other  phenomenon  occur 
in  each  fex,  which  ferve  in  like  manner  to  an- 
nounce the  gradual  approach  of  puberty :  thus, 
in  the  female  the  catamenia  begin  to  flow ;  while 
in  the  male  the  fecretion  of  a  true  femen  com- 
mences, which  is  uniformly  accompanied  by  a 
more  luxuriant  crop  of  beards  and  a  very  ftriking 
change  in  the  voice  from  a  fliriller  to  a  graver 
tone. 

About  the  fame  time  the  fexual injlincl  (§  289.) 
that  fpontaneous  and  potent  call  of  nature,  is  firfi: 
awakened  into  a&ion,  and  man,  now  in  the  blof- 
fom  of  life,  is  fitted  and  inclined  to  venereal  en- 
joyments. 

§  648. 

The  crifis  or  precife  period  of  puberty  cannot 
by  any  means  be  accurately  afcertained.  It  is 
much  varied  by  diverfities  of  climate  and  of  tem- 
perament. In  general,  however,  it  occurs  earlier 
in  the  female  than  in  the  male  fex ;  thus,  in  our 
climate  females  may  be  faid  to  have  arrived  at 
this  interefting  period  againfl  the  fifteenth,  but 
males  not  before  the  twentieth  year  of  life. 

§  649. 


AND  DECLINE  OF  MAN.  207 

§  649. 

Shortly  after  the  above  period  the  human  body- 
finally  ceafes  to  increafe  mjiature ;  this  particular 
is  alfo  influenced  and  greatly  diverfified  by  differ- 
ence of  climate,  not  to  mention  the  countlefs  va- 
rieties that  are  exhibited  relative  to  this  point, 
not  only  by  different  individuals,  but  even  by 
whole  families. 

§  650. 
About  this  period  alfo  the  epiphyfes,  which  had 
been  hitherto  diftinguifhed  from  the  bones  to 
which  they  were  attached  by  very  vifible  lines  of 
feparation,  become  fo  intimately  united  to,  and  fo 
completely  coalefce  with  thefe  bones,  that  not  a 
veftige  is  left  to  ferve  as  a  memento  of  their  for- 
mer didinc'tion. 

§  65I. 
With  refpect  to  the  term  of  perfect  manhood, 
which  conditutes  indeed  the  mod  lengthy,  as  well 
as  mod  ufeful  and  important  period  of  human 
life,  we  find  it  charaSerifed  by  the  higheft  de- 
grees of  vigour  and  uniformity,  when  we  examine 
the  function?  of  the  body,  and  by  that  moft  inva- 
luable prerogative,  maturity  of  judgment,  when 
we  take  into  confideration  the  faculties  of  the 
mind.     Throughout  this  imereding   period   the 

lamp 


:o8      Of  THE  INCREASE,  MATURITY, 

lamp  of  human  life  blazes  with  the  higheft  degree 
of  intenfity  and  fplendor. 

§  652. 
The  heralds  which  unerringly  announce  the  in- 
trufive  approach  of  old  age  are,  in  females,  the 
cefTation  of  the  catamenia,  (§  547. ),  in  males,  a 
languid  propenfity  to  venereal  gratifications,  and 
in  both  an  invafion  of  what  is  called  the  rigidity 
or  drynefs  of  old  age,  with  a  flow  but  fenfible  de- 
clination of  the  vis  vita,  or  aggregate  power  of 
performing  the  various  functions  of  life. 

Finally,  the  frigid  reign  of  the  ultimate  degree 
of  old  age  is  ftrcngly  characterifed  by  the  follow- 
ing concomitant  phenomena,  namely,  a  fluggifh* 
nefs  and  increafmg  dulnefs  of  the  fenfes,  both  ex- 
ternal and  internal,  an  irrefiftible  call  for  longer 
indulgence  in  fleep,  and  a  torpidity  and  languor 
in  all  the  functions  of  the  animal  economy.  The 
hairs  aifume  a  filvery  gray,  and  fall  in  part  from 
their  exalted  fituation.  The  teeth  themfelves 
drop  fpontaneoufly  from  their  declining  fockets. 
The  neck  is  no  longer  able  to  fupport  the  head, 
nor  the  tottering  legs  to  fultain  the  weight  of  the 
incumbent  body.  Even  the  bones  themfelves, 
thofe  indifpenfible  fulcra  of  the  whole  machine, 
1  are 


AND  DECLINE  OF  MAN.  209 

are  obliged  to  bear  a  part  in  this  irremediable 
and  univerfal  decay. 

§  654. 
We  have  thus  arrived  at  length  to  the  remote 
ultimatum  of  phyfiology,  namely,  death  without 
difeafc,  or  the  cuthanafia  of  old  age.  To  conduct 
and  protract  human  life  to  this  only  natural  ter- 
mination (the  caufes  of  which  are  fufticiently  ob- 
vious from  what  has  been  already  laid  down)  con- 
ftitutes  indeed  the  alpha  and  omega,  i.  e.  the  fole 
and  exclufive  end  and  object  of  the  healing  art. 

§    655. 

The  phenomena  of  this  natural  death  (as  obferved 
in  man  when  about  to  refign  himfelf  to  its  potent 
grafp),  are,  a  coldnefs  of  the  extremities,  a  lofs 
of  the  brilliancy  of  the  eyes,  a  very  fmall  and 
flow  pulfe,  accompanied  with  intermiflions  pro- 
greffively  increafmg  in  frequency,  and  laftly  a  flow 
refpiration,  which  by  a  more  forcible  act  of  ex- 
fpiration,  is  at  length  clofed  for  ever. 

In  the  live-diflections  of  animals  belonging  to 
the  clafs  mammalia,  there  is  a  convenient  oppor- 
tunity for  obferving  the  lad  exertions  of  the  heart, 
from  which  it  appears,  that  the  right  ventricle 
and  auricle  of  that  vifcus  refill  the  encroachments 

vol.  11.  O  of 


2io       OF  THE  INCREASE,  MATURITY, 

of  death  longer,  and  continue  the  motions  of  life 
to  a  later  period,  than  the  left. 

§  656. 

Coiclnefs  accompanied  by  rigidity,  a  cadaverous 
flench,  but  more  efpecially  a  flaccidity  of  the  cor- 
nea, and  a  hiatus  or  gaping  of  the  anus  afcertain 
in  the  mod  unequivocal  manner  the  complete  death 
of  the  body.  When  in  the  corpfe  an  aggregate 
collection  of  all  thefe  figns  occur  at  once,  not  even 
the  fceptical  Pliny  himfelf  could  find  room  to  inrer- 
pofe  the  fhadow  of  a  doubt  reflecting  the  complete 
extinction  of  animal  life. 

§  657. 

To  afcertain  with  definitude  the  natural  term  of 
the  life  of  man,  (or  to  point  out  that  period 
which  nny  be  confidered  as  the  more  frequent  and 
regular  goal  or  ne  plus  ultra  of  human  exigence), 
is,  indeed,  a  matter  attended  with  the  utmoft  diffi- 
culty. 1  have  notwithftanding  learnt,  from  exa- 
mining with  care  and  comparing  with  accuracy,  a 
great  number  of  bills  of  mortality,  that  a  confider- 
able  proportion  of  fuch  Europeans  as  are  advanced 
ia  years  reach,  but  that  very  few  of  them  pafs, 
1  :ie  eightieth  and  fourth  year  of  life. 

§  658. 


AND  DECLINE  OF  MAN.  211 

§  658. 
We  may  obferve  upon  the  whole,  that  in  con- 
fequence  of  the  weaknefs  and  tender  fufceptfbility 
of  infancy  and  childhood,  the  intemperance  and 
irregularity  of  an  infinitude  of  adults,  the  incon- 
trolable  violence  of  difeafes,  and  a  countlefs 
multitude  of  fatal  cafualties,  not  more  of  mankind 
than  feventy  eight  in  a  thoufand  refign  their  lives 
to  that  fpecies  of  death  now  under  confideration, 
namely,  death  without  difeafe.  Notwithstanding 
the  truth  and  authenticity  of  the  preceding  obfer- 
vation,  yet  on  making  a  genuine  eftimate  of  human 
longevity  and  comparing  it,  under  fimilar  circum- 
ftances,  with  that  of  the  other  fubjefts  belonging 
to  the  clafs  mammalia,  whofe  natural  term  of 
exigence  is  known  to  us,  it  will  evidently  appear, 
that,  except  the  bafelefs  declamations  of  fop  hi/is 
regarding  the  miferies  of  human  life,  nothing  can 
be  more  unfounded  and  irrational  than  their  fplen- 
did  and  verbofe  effufions  refpe&ing  its  brevity. 


O  o. 


APPENDIX, 

IN   WHICH    IS    EXHIBITED  A 

Condenfed  and  Summary   View 

OF    THE 

EXISTING  DISCOVERIES  AND  SPECULATIONS 

Relative  to  the  Subject  of,  what  is  ufually  denominated, 

ANIMAL  ELECTRICITY. 


STEADY  and  uniform  as  the  lapfe  of 
time  itfelf,  are  the  exertions  made  by  the  enter- 
prize  and  induftry  of  man,  to  fhed  light  on  the 
arcana  or  fecret  proceffes  of  nature.  In  proportion 
as  fuch  laudable  attempts  are  profecuted  with 
boldnefs  and  crowned  with  fuccefs,  revolutions  and 
improvements  take  place  in  the  various  branches 
of  phyfical  fcience.  Revolutions  derive  birth  from 
the  detection  of  error,  while  improvements  refult 
from  the  difcovery  of  truth.  On  the  repudiation 
of  falfe  principles  in  fcience,  as  well  as  on  the 
developement  of  new  ones  deduced  from  the  reci- 
O  3  procal 


214  APPENDIX. 

procal  concurrence  of  numerous  and  unequivocal 
facts,  it  is  not  without  the  Sanction  of  reafon  and 
propriety  that  new  fyftems  are  forthwith  compiled, 
digefted.  and  ufhcred  into  the  world. 

For,  to  be  complete  and  fatisfadtory,  a  fyftem 
in  any  branch  of  fcience,  Should  embrace  and  ar- 
range in  order  all  the  well  authenticated  principles 
fpontaneoufly  refulting  from  facts  already  afcer- 
tained  and  obfervations  already  made,  relative  to 
that  particular  branch.  A  fyftem  lefs  general  and 
comprehenfive  in  its  fcope  than  this,  fhould  be 
deemed,  at  beft,  but  defective  and  partial,  and 
received  as  the  abortive  production  of  a  mind 
deficient  in  point  of  information. 

Of  the  former  defcription  was  the  famous  phy- 
siological fyftem  of  Baron  Haller,  at  the  time  its 
iliuftrious  author  firft  fubmittcd  it  to  the  eye  of  the 
world.  That  excellent  phyfician  and  philofopher 
grafped  in  his  acute  and  comprehenfive  mind,  and 
detailed  at  large,  in  the  work  to  which  I  here 
allude,  all  the  authentic  and  well  defined  princi- 
ples refulting  from  the  infinitude  of  facts  with 
which  the  fcience  of  phyfiology  was  at  that  time 
enriched. 

But  all  fyftems  are  Stationary  and  have  been  as 
yet  imperfect,  while,  happily  for  the  intereft  of 

man, 


APPENDIX  2t$ 

man,  improvements  in  fcience  are  progreffive  and 
advancing  towards  perfection.  In  the  courfe  of  a 
few  years,  fuch  a  blaze  of  phyfical  light  was  dif- 
fufed  abroad  by  the  induflry  and  ingenuity  of 
philofophers  in  general,  but  of  phyficians  and 
cheittifts  in  particular,  that  the  deficiencies  and 
errors  of  the  Baron's  elaborate  fyftem  were  ren- 
dered obvious  to  the  mod  weak  and  inattentive 
obferver.  In  the  important  doclrines  refpe&ing 
the  caufes  of  animal  heat  and  the  nature  and 
purpofes  of  refpiration,  in  particular,  entire  revolu- 
tions were  efft&ed  by  the  numerous  and  ingenious 
difcoveries  of  chemhts  in  that  branch  of  fcience 
denominated  aerology. 

To  fupply,  as  far  as  poflible,  the  deficiencies 
of  this  fyftem  of  Haller,  and  to  circumvent  the 
errors  which  the  authority  of  fo  celebrated  a  cha- 
racter might  tend  to  diffnfe  throughout  the  minds 
of  his  numerous  readers,  became  defiderata  of  no 
fmall  moment  in  the  fcience  of  phyfiology. 

The  mod  effectual  method  of  accompliihing  thefe 
defirable  ends  was  too  obvious  to  efcape  difcovery. 
For  as  violence  is  mod  effectually  repelled  by 
counter  violence,  and  one  difeafe  not  ^infrequently 
removed  from  the  animal  fyftem  by  the  impetuous 
invafion  of  another,  fo  in  like  manner.,  in  fcience, 
the  defects  of  one  fyftem  are  moft  advanrageoufly 
O  4  fupplicd 


ii6  APPENDIX. 

fupplied,  and  its  errors  moft  effectually  contrc- 
verted  and  expoftd,  by  the  plenitude  and  unequi- 
vocal certainty  cf  the  principles  of  a  rival  fyftem. 

This  truth  did  not  efcape  the  obfervation  of  that 
learned  and  acute  profeffbr,  of  Goettingen,  who 
new  fills  the  chair  which  was  formerly  rendered 
vocal  by  the  eloquence  of  the  immortal  Haller. 
Need  I  add,  that  profeffor  Blumenbach  is  the  man 
to  whom  I  allude — a  man,  for  the  completion  of 
whofe  greatnefs  and  utility  in  phylical  fcience, 
nature  and  art  appear  to  have  all  but  exhaufted 
their  abundant  refources !  For  induitry  and  perfe- 
verance  in  the  collection  of  materials,  for  powers 
to  combine  and  arrange  materials  when  thus  col- 
lected, and  for  ingenuity  and  acumen  to  deduce 
and  fpeculate  from  fuch  combination  and  arrange- 
ment, the  prefent  age  certainly  boafts  few-r-too 
few  phyfioiogifts  who  may  be  fee  in  competition 
with  the  illuftrious  Blumenbach. 

For  this  phyfician  and  philofopher  was  referved 
the  honourable  and  important  taH:  of  collecting, 
digefting  and  consigning  to  publicity,  a  fyftem  of 
phyfiology  clefiined  to  fupply  the  deficiencies  and 
correct  the  errors  of  that  which  had  already 
refulted  from  the  labours  or  hi-j  celebrated  friend 
:kpA  predeceiTor.  The  fyftem  of  profeifor  Blumen- 
bach. was,  like  that  of  Baton  Haller,  perfect:  and 

complete 


APPENDIX.  217 

complete  at  the  time  in  which  it  was  handed  to 
the  world.  There  exifted  not,  at  that  period,  an 
eftabli fned  principle,  nor  fcarcely  even  a  probable 
conjecture  in  phyfiology,  with  which  he  was  not 
minutely  acquainted,  and  which  he  did  not  draw 
into  the  extenfive  and  powerful  vortex  of  his 
fyflem. 

Had  the  fcience  of  phyfiology  been  finally  com- 
plete at  the  time  in  which  proieflbr  Blumenbach 
wrote,  the  induftry,  the  immenfe  refources  and 
the  ccmprehenfive  talents  of  that  philrfopher 
would,  no  doubt,  have  quire  precluded  the  necef- 
fity  of  future  fy (terns  in  this  branch  of  fcience. 
But  in  the  unfathomed  depths  of  the  animal 
economy  more  arcana  yet  exifted — more  terra 
incognita  lay  yet  unexplored,  and  further  re- 
fearches  of  enterprise  were  therefore  effenthiLi 

By  the  combined  labours  of  experimental  phyfi- 
ologids  in  different  parts  of  the  world,  this  branch 
of  fcience  was  at  length  matured  for  giving  birth 
to  another  difcovery,  which  will  probably  be  found 
of  equal  importance,  in  explaining  the  phenomena, 
and  in  removing  the  difeafes  of  the  animal  fyflem, 
with  that  which  consigned  to  immortality  the  name 
of  the  illuftrious  Harvey.  The  difcevcry  to  which 
I  wifli  at  prefent  to  direct  the  attention  of  the 
reader  is  that   of,  what  is  ufua'.ly  called  animal 

>  V'7;  Icity. 


t\%  APPENDIX. 

elcclricity,  or,  of  the  exigence  and  operation  of  a 
fluid  extremely  fimilar  to  electricity  in  the  living 
animal  fyftem.  For  the  fortunate  Galvani  pro- 
felfor  of  anatomy  at  Bologna,  was  referved  the 
honour  of  lighting  by  accident  on  this  beautiful 
and  divine  difcovery — a  difcovcry  which  entitles 
its  author  to  be  ranked  with  the  great  promoters 
fcience  and  the  enential  benefactors  of  man. 

That  fuch  a  fluid  did  actually  exiit  in  the  bo- 
dies of  animals,  had  been  long  fufpe&ed  by  phy- 
fiologifts  and  other  fpeculative  philofophers.  The 
matter  refted  however  on  pure  conjecture  alone, 
and  was  yet  unfan&ioned  by  the  tefls  of  experi- 
ment and  obfervation.  The  apparent  intricacy 
of  the  fubject  deprelfed  the  hopes  of  the  boldefl 
experimenters,  and  the  fubtlety  of  the  investiga- 
tion feemed  to  throw  an  infurmountable  bar  in  the 
road  to  fuccefs.  But  accident  not  unfrequently 
does  more  for  the  real  advancement  of  fcience, 
than  boafled  genius  and  induftry  are  able  to  ac- 
complifh.  It  was  accident  that  firft  fuggefted  to 
the  celebrated  Gallileo  the  conftruction  and  ufe 
of  that  optical  inftrument  denominated  the  tele- 
fcope—It  was  accident  which  firft  led  the  immortal 
Newton  to  the  original  conception  of  that  prin- 
ciple of  gravitation,  by  which  he  afterwards  ex- 
plained, with  fuch  facility,  the  movements  and  ex- 
quifite  balance  of  the  material  univerfe.     And  it 

was* 


APPENDIX.  219 

wis,  in  like  manner,  accident — fortunate  accident, 
that  firft  fuggefted  to  the  induftrious  and  acute 
Galvani  the  mode  of  experimenting,  with  effect, 
on  the  intricate  fubjecl  of  animal  eledricity—2. 
fubje<ft  which  may  poffibly  be  deftined  as  the  only 
proper  clue  to  conduct  future  phyfiologifts  to  the 
genuine  fprings  and  principles  of  life  itfelf. 

"  Whilfl  the  profeflbr  (alluding  to  Galvani) 
was  engaged  in  drfTe&ing  a  frog  in  a  room  where 
fome  of  his  friends  were  amufing  themfelves  with 
an  electrical  machine,  one  of  them  drew  a  fpark 
from  the  conductor,  at  the  fame  time  that  the 
profeffor  touched  one  of  the  nerves  of  the  animal. 
In  an  jnftant  the  whole  body  of  the  frog  was 
fhook  by  a  violent  convulfion.  The  profeiTor 
was  aftonifhed  at  the  phenomenon,  and  believed 
it  owing  to  his  having  wounded  the  nerve  ;  to 
affure  himfelf  whether  this  was  really  the  cafe, 
he  pricked  it  with  the  point  of  his  knife,  without 
any  motion  of  the  body  being  produced  ;  he  how 
touched  the  nerve  with  the  inftrument  as  at  firft, 
and  ordered  a  fpark  to  be  taken  from  the  machine, 
on  which  the  contractions  were  renewed.  The 
experiment  was  repeated  a  third  time,  but  the 
animal  remained  motionlefs ;  however,  upon  per- 
ceiving he  held  his  fcalpel  by  the  handle,  which 
was  of  ivory  (a  bad  conductor),  he   changed  it 

for 


—  APPENDIX. 

for  a  metallic  one,  and  re-excited  the  movements,- 
which  he  conftantly  failed  of  doing  whilft:  ufing 
an  electric  fubftance. 

"  After  having  made  a  number  of  experiments 
with  the  elect  ical  machine,  he  refolved  to  profe- 
cute  the  fubject  with  atmofpheric  electricity.  To 
this  end  he  raifed  a  conductor  upon  the  roof  of 
his  houfe,  from  which  he  brought  an  iron  wire 
into  his  room,  and  to  this  attached  metal  con- 
ductors, connected  with  the  nerves  of  the  animals 
defined  to  be  the  fubjects  of  his  experiments, 
and  to  their  legs  he  tied  wires,  which  reached  the 
floor.  Confiderable  movements  were  obferved  in 
the  animals,  whether  of  cold  or  warm  blood, 
whenever  it  lightened.  Thefe  preceded  thun- 
der, and  corrtfponded  with  irs  intenfity  and  re- 
petition, and  even  when  it  did  not  lighten  the 
movements  took  place  when  any  florniy  cloud 
palled  over  the  apparatus." 

"  Profeffor  Galvani  one  day  lufpended  fome 
frogs,  perhaps  with  fimilar  views,  on  metal  hooks, 
fixed  in  the  fpiric  of  the  back,  upon  the  iron  rail- 
ing of  his  garden  ;  feveral  times  he  remarked  that 
thefe  animals  contracted,  and  appeared  to  receive 
fhocks ;  at  firft  he  conceived  the  movements  were 
owing  to  changes  in  the  atmofphere,  but  a  more 

fcrupulous 


APPENDIX.  22} 

icrupulous  examination  undeceived  him*  Having 
placed  a  prepared  frog  *  upo:i  an  iron  plate  in  his 
room,  and  happening  with  his  differing  forceps  to 
prefs  it  againfl  the  plate,  he  obferved  the  move- 
ments to  take  place.  This  experiment  fuccecded 
with  all  metallic  bodies,  but  more  particularly  well 
with  filver ;  non-conducing  fubftances  were  not 
proper  for  it.  From  this  period  our  author  began 
to  fuipeft  the  animal  pofTefTcd  an  electricity  of  its 
own  ;  and  in  this  fufpicion  he  was  further  con- 
firmed by  the  following  circumftance  : — He  held 

*  That  the  reader  may  not  be  entirely  ignorant  of  what  is 
meant  by  a  prepared  frog,  I  take  the  liberty  of  prefenting 
him  with  the  following  brief  extract  from  the  firft  experi- 
ment detailed  in  Dr.  Valli's  publication  :  "  My  firft  experi- 
ment was  made  on  a  frog,  in  the  following  manner  :  I  opened 
the  abdomen  in  order  to  lay  bare  the  fpine  of  the  back,  and 
difcover  the  crural  nerves  which  i.Tue  from  it ;  a  few  lines 
above  this  point  I  cut  the  animal  in  two,  and  by  p  ailing  my 
fciilars  immediately  under  the  origin  of  thefe  nerves,  re- 
moved the  remaining  portion  of  the  vertebral  column,  fo 
as  only  to  leave  the  vertebra:  which  united  the  bundle  of 
nerves.  Having  enveloped  this  portion  of  the  vertebra  with 
a  piece  cf  ftiee';  lead,  with  one  end  of  a  metal  conduflor,  I 
touched  the  coated  part,  and  with  the  other  the  furface  of 
the  thighs,  which  had  been  previously  ftripped  of  the  fkir. 
The  movements  were  violent,  and  continued  for  a  long  time," 
&c.  In  general,  throughout  the  whole  of  tlvs  phyfician's 
expertmental  treatife,  when  one  cr  more  of  the  nerves  of  an 
animal  arc  coated  with  (heet-lcad  or  any  ether  metal,  that 
animal  is  faid  to  be  prepared, 

to 


it*  APPENDIX. 

a  prepared  frog  by  a  hook  with  one  hand,  (o  as 
to  let  its  feet  reft  upon  the  bottom  of  a  fraall  fil- 
ver  cup,  which  he  happened  unintentionally  to 
ftrike  with  the  other  ;  at  the  inftant  the  body  of 
the  animal  fell  into  violent  convulfions.  If  one 
perfoa  held  the  prepared  frog,  and  another  touch- 
ed the  cup,  no  movements  were  excited.  The 
profeflbr  being  now  aware  of  the  neceffity  of  a 
communication,  undertook  a  feiies  of  experiments 
for  the  farther  investigation  of  this  fubject.  He 
firft  placed  a  prepared  frog  upon  a  non-conduct- 
ing furface,  and  brought  one  end  of  a  conductor 
in  contact  with  the  hook  which  fecured  the  ani- 
mal, and  with  the  other  touched  its  feet,  on  which 
the  contractions  took  place.  When  the  conduct- 
ing arch  was  interrupted  by  a  non-conducting 
fubftance,  the  frog  remained  motionlefs,  &c." 

No  fooner  hadproftlTor  Galvani  publifhed  to 
the  world  his  experiments  en  animal  electricity, 
than  their  fame  difpread,  fwift  us  the  intangible 
fluid  which  they  regarded,  throughout  the  differ- 
ent parts  of  Europe.  Animal  electricity  became, 
in  a  fhort  time,  a  fubject  of  very  interefting  fpecu- 
lation  to  medical  philofophers.  Among  the  feve- 
ral  phyfiologifts  who  entered  the  lifts  in  this  in* 
veftigation,  the  molt  diftinguifhed  whofe  writings 
have  fallen  into  my  hands,  are  Dr.  Valli,  an  Italian 
phyfician,  from  whofe  publication  the  preceding 

account 


APPENDIX.  223 

account  refpe&ing  the  firft  difcoveries  of  Galvani 
is  extracted,  and  Mr.  Fowler,  a  native  of  the 
ifland  of  Great  Britain. 

Do£tor  Valli  appears  to  have  led  the  van  of 
thofe  philofophical  characters  who  firft  co-ope- 
rated with  the  celebrated  Galvani  in  inveftigating 
that  animal  fluid,  the  exigence  of  which  had  been 
{o  long  fufpefled,  but  fo  lately  realifed  by  actual 
experiment.  After  repeating  mod  of  the  experi- 
ments of  his  predeceffor  in  this  branch  of  phyfics, 
the  Doclor  proceeded  to  a  feries  of  new  experi- 
ments, moftly  conceived  and  inftituted  by  himfelf. 

The  objects  which  he  appears  to  have  kept  flea- 
dily  in  view  throughout  the  whole  courfe  of  his 
experiments  and  obfervarions  were,  to  afcertain 
the  nature  of  the  animal  fluid  difcovered  by  the 
profeflbr  of  Bologna,  and  to  determine  its  influ- 
ence and  medium  of  operation  in  the  animal  eco- 
nomy. In  the  profecution  of  thefe  ends  the  Doc- 
tor has  doubtlefs  difplayed  all  that  iuduftry  and 
patient  perfeverance,  (o  eflentially  requisite  in  the 
character  who  would  fuccefsfully  inquire  of  na- 
ture, through  the  medium  of  experiment.  I  am 
forry  ,however,  to  obferve,  that  all  his  experiments 
were  not  conceived  and  inflituted  with  equal  in- 
genuity, and  perhaps  I  may  add,  not  executed 
•with  equal    accuracy  and   defmitude.     Many   of 

many 


224  APPENDIX. 

them  appear  to  have  been  indituted  without  a  di- 
rect reference  to  any  fpecific  or  particular  end — 
Equally  unhappy  with  regard  to  conception,  inde- 
finite with  refpeft  to  their  nature,  and  inconclu- 
sive in  point  of  refult,  they  leave  no  imprefflons 
on  the  mind  of  the  reader,  five  thofe  of  d'tfap- 
poiniment  and  regret — regret  that  a  character  of 
fuch  learning  and  induftry  ihould,  notwithdand- 
ing,  interrogate  nature  with  fo  little  meaning,  and 
(I  am  forry  to  add)  with  fo  little  fuccefs. 

The  preceding  obfervations  mud  be  confidered 
only  in  the  light  of  general  rules,  and  as  fuch, 
are  liable  to  numerous  exceptions.  Many  of  the 
experiments  of  Dr.  Valli  are,  doubtkfs,  both  in- 
genious and  valuable  ;  and  I  even  entertain  the 
utmoft  confidence,  that  the  period  will  yet  arrive, 
when  the  whole  of  them,  that  are  afcertained 
and  related  with  juflnefs  and  definitude,  will  be 
made  fubfervient  to  the  eilablifhment  of  general 
and  ufeful  remits.  At  prefer)  t,  however,  they 
(land  in  an  infalaled  date,  completely  detached 
from  practical  conclufions,  and  difconnected  from 
all  known  principles  in  phyfical  feience. 

After  a  feries  of  experiments  fufliciently  lengthy 
and   tedious,  the  Doctor  conceived  himfeif  une- 
quivocally authorifed  to  conclude,  that  the  animal 
fluid  of  Galvani,  was  entirely  the  fame  with  the 
4  fu1—  I 


APPENDIX.  225 

fubtle  matter  of  electricity.  This  conclufion  he 
alleges  to  be  the  fpontaneous  and  necefiary  refult 
of  the  following  pofitions,  which  he  delivers  as 
fubftantiated  and  confirmed  by  actual  experiment. 

"  Firft,  fubftances  which  conduct  electricity, 
are  conductors  likewife  of  the  nervous  fluid." 

"  idly,  Subftances  which  are  not  conductors 
of  electricity,  do  not  conduct  the  nervous  fluid.'* 

"  3^//y,  Non-conducting  bodies,  which  acquire 
by  heat  the  property  of  conducting  electricity, 
preferve  it  likewife  for  the  nervous  fluid." 

"  Atbly,  Cold  at  a  certain  degree,  renders  water 
a  non-conductor  of  electricity,  as  well  as  of  the 
nervous  fluid." 

"  $thly,  The  velocity  of  the  nervous  fluid  is, 
as  far  as  we  can  calculate,  the  fame  with  that  of 
electricity." 

"  6thly,  The  obflacles  which  the  nerves,  under 
certain  circumflances,  oppofe  to  electricity,  they 
prefent  likewife  to  the  nervous  fluid." 

"  ytbly,  Attraction  is  a  property  of  the  electric 
fluid,  and  this  property  has  been  difcovered  in  the 
nervous  fluid." 

vol.  11.  P  Having 


226  APPENDIX. 

Having  enumerated  and  detailed  the  foregoing 
arguments,  the  Doctor,  in  an  erfufion  of  triumph, 
fubjoins,  "  We  here  fee  the  greateft  analogy  be- 
tween thefe  fluids ;  nay,  I  may  even  add,  the  cha- 
racters of  their  identity." 

As  an  additional  fupport  to  the  fame  opinion, 
Dr  Valli  adduces  the  peculiar  and  ftriking  pheno- 
mena exhibited  by  the  torpedo,  the  gyninotus  elec- 
trieus,  the  Jilurus,  &c.  which  proceed,  as  he 
alleges,  from  a  fluid  in  every  refpect  the  fame 
with  that  which  was  difcovered  in  frogs,  by  the 
profeflfor  of  anatomy  at  Bologna.  As  the  Doctor, 
however,  has  advanced  nothing  in  confirmation  of 
fuch  entire  famenefs,  fave  a  certain  remote  analogy 
which  he  fays  he  has  difcovered  between  the  muf- 
cles  of  animals,  and  the  electrical  apparatus  of  the 
torpedo,  the  gymnotus,  &c.  it  is  obvious  that  this 
latter  argument  will  but  very  flightly  imprefs  the 
philofophical  phyfiologift,  who  founds  his  belief 
of  principles  on  facls,  rather  than  on  vague  and 
vifionary  conjectures. 

Having  thus,  as  he  fuppofed,  fatisfactorily  afcer- 
tained  the  identity  of  the  nervous  with  the  electric 
fluid,  he  next  proceeds  to  fpeculations  on  its  in- 
fluence in  the  diverfified  movements  and  functions 
of  the  animal  economy.  To  me,  however,  I  mud 
confefs,  the  greater  part  of  this  fpeculative  invef- 
ligation,   appears  to  be  rather   the  eflervefcent 

effufions 


APPENDIX.  227 

effufions  of  an  imagination,  heated  to  excefs  in  a 
favourite  purfuir,  than  the  folemn  decifions  of  a 
tranquil  and  unbiafTed  under/landing.  I  acknow-> 
ledge  myfelf  unable,  in  many  inftances,  to  difcern 
the  necefTary  nexus  or  affinity  between  his  con- 
clufions,  and  the  fa&s  from  which  they  are  de- 
duced : — or  perhaps  I  may  fpeak  my  fentiments 
more  fully  when  1  fay,  that  the  learned  author 
appears  not  unfrequcntly  to  have  fubftitutcd  mere 
hypothetical  allegations,  for  fair  and  logical  conclu- 
fions — the  vacant  refults  of  his  own  conjectures, 
for  genuine  principles  developed  by  experiment, 
and  afcertained  by  obfervation.  It  very  often 
happens,  that  by  attempting  to  embrace  too  much 
under  a  fingle  caufe,  we  extend  the  tortured 
principle  beyond  its  natural  limits,  and  thus,-  to 
appearance,  weaken  or  render  doubtful  its  influ- 
ence, even  on  thofe  phenomena  which  it  immedi- 
ately regards.  This  obfervation  applies  with  too 
much  propriety  and  force,  to  the  fpeculations  of 
the  indefatigable  Valli.  By  attempting  to  explain 
all,  he  has  in  fa£t  explained  none,  of  the  pheno- 
mena of  the  animal  economy,  by  that  fubtle  fluid 
on  which  he  fo  patiently  experimented.  Many  of 
his  phyfiological  fatts  and  fpeculations  are  indeed 
ingenious  and  interesting,  but,  in  my  view,  they  are 
equally  deducible  from  any  other  feries  of  experi- 
ments, as  from  that  by  which  they  are  preceded 
in  the  Doctor's  publication.  Many  of  the  learned 
author's  fafts  may  be,  no  doubt,  true  and  well 
P  2  defined 


228  APPENDIX. 

defined,  and  forne  of  his  principles  and  refults  to 
a  certain  degree  interefting  to  the  phyfician  and 
philofopher,  but,  taken  in  the  aggregate,  they 
are  too  diljointed  to  conftitute  any  thing  like  a 
fyftem,  too  difconne&ed  to  form  a  regular  chain 
of  investigation.  On  my  mind,  his  /peculations 
on  the  caufes  of  mufcular  motion,  fenfation  fecre- 
tion  and  nutrition,  imprefs  no  more  folid  convic- 
tion than  do  ihofe  of  Stahl  on  the  fubjeft  of  his 
anima  medica,  of  Van  Helmont  refpe&ing  his 
fubtle  Archeus,  or  of  the  airy  Paracelfus  with  re- 
gard to  his  planetary  influence,  Notwithftanding 
the  apparent  feverity  of  the  foregoing  obferva- 
lions,  I  am  fiiil  obliged  to  declare  it  as  my 
opinion,  that  the  novelty  and  importance  of  the 
fubject  on  which  Dr  Valli  has  experimented  and 
written,  entitle  his  work  to  the  particular  atten- 
tion of  the  learned  and  ingenious  of  every  na- 
tion. 

For  the  want  of  fyftem  and  requifite  decifion  in 
the  writings  of  the  preceding  author,  compenfation 
is,  in  a  great  meafure,  made  by  a  fubfequent  pub- 
lication of  the  accurate  and  ingenious  Fowler.  The 

experiments  and  fpeculations  of  this  young  philofo- 
pher, on  what  he  terms,  the  "  influence  difcovered 
by  Gahani,"  made  their  firft  public  appearance 
at  Edinburgh,  in  the  courfe  of  the  year  1793  : 
they  are  not,  indeed,  fo  numerous  as  thofe  of  the 
Italian  phyfician,  but  they  appear  to  have  been 

conceived 


APPENDIX.  229 

conceived  with  more  defign,  and  executed  with 
more  judgment.  Mr.  Fowler  feems  to  have  been 
among  the  firfl  who  controverted  the  opinion  of 
Galvani  and  Valli,  reflecting  the  identity  of  the 
nervous  and  electric  fluids:  and  he  has,  doubtlcfs, 
controverted  it  with  ability  and  effect. 

Mr.  Fowler  preliminates  his  obfervations,  with 
a  lucid  and  forcible  Statement  of  a  certain  previous 
combination  of  circumftances,  which  he  alleges, 
muff  haveftrongly  prepoflfefTed  the  mind  of  profeffor 
Galvani,  with  a  belief  of  the  famenefs  of  the  pre- 
ceding fluids. 

That  fuch  a  prepoffeflion  mufl  have  had,  indeed, 
a  powerful  effect  on  the  ifubfequent  dedu&ions  and 
conclufions  of  the  Profeffor,  will  be  readily  ac- 
knowledged, by  every  one  who  has  experienced 
the  influence  of  preconceived  opinions — an  influ- 
ence pregnant  with  error,  and  leading  countlefs 
evils  in  its  train. 

Mr.  Fowler  proceeds  then  to  mention  the  firft 
object  which  engaged  his  attention,  in  the  com- 
mencement of  his  interesting  inquiry,  and  which 
appears  well  calculated  to  pave  the  way,  for  the 
more  eafy  and  effectual  accomplishment  of  his 
experimental  courfe.  This,  to  make  ufe  of  his 
cwn  words,  was,  "  to  afcertain,  as  well  the  va- 
P  3  rious 


23®  APPENDIX 

rious  circumftances,  effentially  requisite  to  the 
production  of  thefe  new  phenomena,  as  thofe  in 
which  they  can  be  rendered  moft  obvious."  The 
iflue  of  his  enquiry  on  this  fubj  £t,  1  will  alfo  lay 
before  the  reader  in  his  own  words.  "  After" 
fays  he,  "  a  great  variety  of  experiments,  of  which 
it  wonld  be  unneceffary  here,  to  relate  more  than 
the  refult,  I  found,  that  I  could  not  excite  in  an 
animal  the  appearances  defcribed  by  Galvani,  with 
any  fubftances  whatever,  whether  folid  or  fluid, 
except  the  metals :  and  that  the  mutual  contact  of 
two  different  metals  with  each  other,  fo  far  as  I 
was  able  to  determine,  was  in  every  cafe  neceffary 
to  the  effcc~t." 

After  a  fatisfa&ory  attainment  of  this  object, 
the  ingenious  author  next  proceeds  to  a  judicious 
feries  of  experiments,  with  a  view  to  difcover  the 
genuine  nature  of  the  animal  fluid,  firft  realifed  by 
the  fortunate  profeflfor  of  Bologna.  Of  thofe  ex- 
periments he  does  not  give  us  a  minute  fpecifka- 
tion,  but  only  furnifhes  fhiternents  of  their  moft 
obvious  and  linking  refults.  Thefe  Abatements  he 
alfo  occafionally  interfperfes  with  intertfting  and 
important  remarks,  and  fome  very  ingenious  fpe- 
culations. 

Having  flnifned  his  feries  of  experiments,  (a 
feries  fufiiciently  numerous  and  diverfified  for  the 

eftablifhment 


APPENDIX.  231 

flablifhment  of  general  principles)  relative  to  the 
nature  of  the  nervous  fluid,  and  its  affinity  to  the 
matter  of  electricity,  Mr.  Fowler  at  length  favours 
us  on  this  fubject  with  the  following  conclusions, 
which  I  fhall  take  the  liberty  of  preferring  to  the 
reader  in  the  words  of  their  ingenious  anthor. 

After  having  ftated  a  few  analogies  between  the 
animal  fluid  of  Galvani,  and  that  pofLflfed  by  the 
torpedo,  he  then  reverfes  the  comparifon,  and 
lays  down  feveral  points  of  effential  difference, 
not  only  between  the  two  preceding  fluids,  but 
alfo  between  the  former  of  them,  namely  the  fluid 
of  Galvani,  and  the  matter  of  electricity. 

"  This  influence,  (fays  he,  referring  to  the 
nervous  fluid  of  animals)  differs,  both  from  that 
of  the  torpedo,  &c.  and  from  electricity,  in  pro- 
ducing no  fenfation  (in  man  at  lead)  at  all  fimilar 
to  that  of  an  electrical  {hock." 

" That  fome  kind  of  difaereeable  fenfation 


is  occafioned  by  it,  even  in  frogs,  independent  of 
that  which  mud  neceffarily  arife  from  irritation 
and  the  contractions  of  their  mufcles,  is  evident 
from  their  reflleffnefs  and  expreffions  of  uneafinefs. 
In  other  animals,  as  I  mall  afterwards  have  occa- 
fion  to  fhew,  thefe  expreffions  are  (till  lefs  equi- 
vocal :  and  in  man  we  can  afcertain  both  their 
P  4  degree 


232  APPENDIX. 

degree  and  their  kind.  That  they  differ  confider- 
ably  from  fuch  as  are  produced  by  electricity  will 
be  proved  when  I  come  to  fpeak  of  the  effects  of 
this  influence  upon  our  fenfes." 

<c  But  the  mod:  important,  and  characteristic 
difference  which  I  have  yet  been  able  to  difcover, 
between  this  new  influence  and  electricity,  confifts 
in  their  effects  upon  the  contractile  power  of 
auimals  and  of  plants.  The  contractions  of  ani- 
mals excited  by  electricity  have  a  tendency  to 
deftroy  that  power  upon  which  contractions  de- 
pend. But  the  contractions  excited,  by  the  appli- 
cation of  the  metals,  have,  in  all  my  experiments, 
had  the  directly  oppofite  effect.  The  more  fre- 
quently contractions  have  been  in  this  way  excited, 
the  longer  do  they  continue  excitable  :  and  the 
longer  are  the  parts  upon  which  fuch  experiments 
are  made,  preferved  from  putridity.  An  influ- 
ence, capable  of  exciting  contractions  without 
occafioning  exhauflion,  was  a  thing  I  fo  little 
expected  to  find,  and  fo  contrary  to  the  character 
which  had  been  given  of  this  both  by  Galvani 
and  by  Doctor  Valli,  that  I  at  flrfl  diftrufted  my 
own  observation  of  the  fact :  but  the  number  of 
comparative  experiments  which  I  had  afterwards 
cccafion  to  make,  though  with  views  different 
from  that  of  afcertaining  the  point  in  queftion, 
convinced  me  that   this   influence,   fo   far   from 

deftroyjng 


APPENDIX.  233 

deftroying  the  contractility  of  mufclcs,  has  a  ten- 
dency to  preferve  it.  Oxygene  is,  fo  far  as  I 
know,  the  only  ftimulus  in  nature,  whofe  effects 
are  at  all  analogous." 

"  When  a  frog  has  been  long  dead,  I  have 
been  fometimes  more  than  a  quarter  of  an  hour 
without  being  able  to  excite  a  fingle  contraction 
by  the  application  of  the  metals :  but  after  this, 
without  at  all  varying  the  means  employed,  con- 
tractions have  appeared,  and  have  become  gradu- 
ally more  and  more  vigorous. " 

"  It  is  laid  (for  I  have  never  had  an  opportunity 
of  making  the  experiment),  that  a  dream  of  elec- 
tricity, palTed  through  a  fenfitive  plant,  produces 
an  almoft  immediate  collapfe  of  its  leaves.  But 
the  influence  difcovered  by  Galvani  produced  no 
fuch  effect  in  the  following  experiment.  Having 
feparated  the  leg  of  a  frog  from  its  body,  I  freed 
its  crural  nerves  from  furrounding  parts,  and  with 
one  hand  held  it  fupported  upon  the  end  of  a 
probe.  An  afliftant  placed  a  piece  of  filver  under 
its  foot,  and  held  the  zinc  with  which  it  was  to 
be  touched,  A  fenfative  plant  formed  the  medium 
of  communication  between  us.  He  held  the  bot- 
tom of  its  (tern  between  his  fingers,  while  I  held 
the  top ;  fo  that  when  the  filver  was  touched  by 
the  zinc,  the  influence  paffed  tip  the  plant,   and 

through 


234  APPENDIX. 

through  the  whole  of  its  ftem.  The  frog's  teg 
inftantly  contracted,  and  repeated  its  contractions 
every  time  the  filver  and  zinc  were  brought  in 
contact :  but  the  leaves  of  the  plant  did  not  col- 
lapfe  ;  neither  did  they  when  any  of  its  branches 
formed  part  of  the  circuit." 

I  mufl  however,  confefs  that  the  plant,  upon 
which  this  experiment  was  made,  had  been  kept 
through  the  winter.  With  a  young  one  the  refult 
might  poflibly  be  different ;  but  fuch  an  one  I 
have  not  yet  had  in  my  power  to  procure. 

"  The  torpedo  does  not  appear  at  all  affected 
by  the  influence  which  itfelf  produces.  Animals 
in  which  Galvani's  phenomena  are  produced,  are 
ftrongly  affected." 

The  very  ingenious  author  paffes  on  next  to 
report  the  refult  of  certain  experiments  which  he 
inflituted,  in  order  to  refute  the  opinion  of  thofe, 
who  allege,  that  the  fluid  of  Galvani  proceeds 
entirely  from  the  metallic  fubftances  ufcd,  and 
does  not  refide  at  all  in  any  part  of  the  animal 
fyftem.  In  his  enquiry  refpecting  this  point  he 
difplays  the  fame  fertility  in  devifing,  the  fame 
fagacity  in  judging,  and  the  fame  ingenuity  in 
deducing,  which  fo  forcibly  imprefs  the  reader 
throughout  every  part  of  his  experimental  invefti- 

gation. 


APPENDIX.  235 

gation.  He  alfo  farther  {hows,  that  the  nervous 
influence  of  Galvani,  and  the  fubtle  fluid  of  elec- 
tricity differ  very  materially  from  each  other  in 
the  following  particular,  namely,  that  againft  the 
effects  of  the  former,  animals  are  able  to  guard 
thcmfelves  by  means  of  a  certain  voluntary  exer- 
tion, whereas  the  operation  of  the  latter  is  not  in 
the  fmalleft  degree  fubjeft  to  the  controul  or  in- 
fluence of  the  will. 

Having  fmifhed  the  confederation  of  the  nature, 
Mr.  Fowler  proceeds  to  make  fome  ufetul  appli- 
cations ^  of  the  influence  difcovered  by  the  profeflfor 
of  anatomy  at  Bologna.  In  his  attempts  to  ftied 
light  on  certain  controverted  points,  and  to  folve 
certain  abflrufe  qneftions,  in  phyfiology,  by  means 
of  this  fluid,  he  appears  no  lefs  ingenious  and 
fatisfa&ory  than  in  the  former  parts  of  his 
enquiry. 

He  appears  peculiarly  happy  and  conclufive  in 
his  refearches  after  the  fource  from  whence  the 
nerves  and  mufcles  derive  their  refpe&ive  powers. 
I  beg  leave  to  lay  before  the  reader  two  of  the 
author's  experiments,  inflituted  for  the  purpofe  ot 
afcertaining  this  interefting  particular — a  particular 
which  has  fo  long  furnifhed  a  fubjeft  of  Gontro- 
verfy  among  fpeculative  phyGologifts.  The  latter 
of  the  two  experiments,  (to  which  the  former 

ferves 


2^6  APPENDIX. 

ferves  only  as  a  necefTary  introdu&ion)  is  of  itfelf 
more  than  equal  to  all  that  has  ever  been  ad- 
vanced on  the  oppofke  fide  of  the  queltion. 

Experiment  I. 
"  I  divided  (fays  Mr.  Fowler)  the  fciatic  nerve 
of  one  leg,  and  tied  the  crural  artery  of  the  other 
in  a  large  frog.  Scarcely  any  blood  was  loft  in 
doing  either.  Two  days  after  this  I  ftrangled  it. 
During  the  firft  24  hours,  the  leg  in  which  the 
nerve  had  been  divided,  appeared  to  contract  with 
the  mod  vigour;  after  this  period  the  difference 
between  them  became  more  doubtful;  but  the 
contractions  were  at  no  time  ftronger  in  the  leg 
whofe  artery  was  tied,  than  in  that  whofe  nerve 
was  divided. 

Experiment  II. 

"  The  fame  operations  were  performed  upon  a 
large  female  frog  full  of  fpawn.  Four  hours 
afterwards  {he  was  covered  by  a  male,  who  had 
been  treated  in  a  fimilar  manner.  I  mention  this 
circumftance,  as  it  tends  to  prove,  that  the  pain 
occafioned  by  the  operation  was  probably  not  fo 
great  as  to  produce  much  fallacy. 

"  On  the  day  following,  (lie  had  fpawned,  and 
on  the  fixth  day  from  the  operations,  me  was 
Wrangled.     When  laid  upon  a  plate  of  zinc,  and 

excited 


APPENDIX.  237 

excited  by  means  of  a  rod  of  filver,  the  contrac- 
tions were  found  extremely  feeble  in  the  leg 
whofe  artery  had  been  tied,  and  ceafed  altogether 
in  about  twenty-two  hours  after  her  death. 

In  the  leg,  whofe  nerve  had  been  divided,  they 
appeared  as  vigorous  as  they  ufually  are  in  legs 
to  which  no  injury  has  been  previoufly  done,  and 
continued  excitable  upwards  of  two  days  after 
they  had  ceafed  to  be  fo  in  the  other.'* 

It  may  be  proper  on  the  prefent  occafion  briefly 
to  obferve,  that  the  influence  difcovered  by  Gal- 
vani  was  the  tefl  ufed  by  Mr.  Fowler  to  determine 
the  exiftence  or  ceffation  of  irritability  in  the 
mufcles  of  the  animals  fubje&ed  to  the  preceding 
experiment.  For  this  influence,  as  our  author 
judicioufly  obferves,  appears  to  be  indeed  by  far 
the  beft  and  moft  delicate  tefl:  that  has  ever  yet 
been  difcovered  for  afcertaining  the  loweft  poflible 
degrees  of  mufcular  irritablility.  After  having 
become  wholly  infenflble  to  the  impreflions  of  all 
other  flimuli,  mufcles  flill  continue  to  vibrate  to 
the  kindred  touches  of  this  fubtle  fluid,  to  which 
nature  appears  to  have  given  them  fuch  a  nice, 
and,  perhaps  I  may  fay,  fpeciflc  correfpondence. 

Mr.   Fowler,  after  having  tranfiently  glanced 
on  the  fubjeft  of  inflammation,  pafles  on  to  the 

attack 


238  APPENDIX. 

attack  of  a  phyfiological  doctrine,  propagated  with 
zeal,  and  fupported  with  ability  by  that  celebrated 
experimentalift,  the  Abbe  Fontina.  The  doctrine 
alluded  to,  embraces  the  exiftence  or  refidence  of 
a  certain  vital  principle  in  the  volume  of  the 
blood.  On  this  principle,  as  the  induftrious 
Abbe  alleges,  poifons  produce  their  inflantaneous 
effect,  when  introduced  into  the  vafcular  fyftems 
of  living  animals.  To  all  the  different  parts  of 
this  phyfical  doctrine  I  could  never  yet  be  induced 
to  fubfcribe,  notwithstanding  the  refpectability  of 
its  learned  and  numerons  advocates. 

By  attacking  and  vanquifhing  one  of  its  mofl 
powerful  champions,  Mr.  Fowler  has  doubtlefs 
contributed  much  to  its  final  demolition.  For,  in 
the  conteft  now  under  our  immediate  confide- 
ration,  I  mud  confefs,  that  to  me  the  laurels  of 
victory  appear  to  be  fairly  wrefted  from  the 
filvered  temples  of  the  Italia?i,  and  planted  over 
the  youthful  brow  of  the  BritiJJj  Philofopher. 

I  have  thus  exhibited  a  view,  fomewhat  general 
indeed,  though  confeffedly  very  fuccinct,  of  the 
refults  laid  down,  and  of  the  opinions  entertained, 
by  the  ingenious  Fowler,  on  the  fubjeet  of  the 
animal  influence  difcovered  by  ProfefTor  Galvani. 
To  lay  before  the  reader  a  full  account  of  all  that 
is  ufeful  and  important  in  the  obfervations  of  this 

imereflin<s 


APPENDIX.  239 

interefting  author,  would  be  to  tranfcribe  and  re- 
print his  whole  publication. 

The  only  productions  in  the  Englifh  language, 
whirh  this  country  now  furnifhes,  profefLdly  on 
the  fubjeft  of  the  animal  fluid  difcovered  by  Gal- 
vani,  are  (as  formerly  obferved)  thofe  of  Fowler 
and  Va Hi.  On  the  comparative  merit  of  thofe 
two  authors  I  will  here  take  the  liberty  of 
advancing  a  few  general,  and,  I  flatter  myfelf, 
impartial,  obfervations : 

The  experiments  of  Doctor  Valli  are  more 
numerous  and  pompous — thofe  of  Mr.  Fowler 
more  definite  and  intelligible.  The  former  aurhor 
appears  often,  the  latter,  never,  to  have  experi- 
mented without  fome  determinate  end  in  view. 
The  experiments  of  the  Italian  may  be  compared 
to  the  promiscuous  plants  of  the  foreft,  ftrewn  at 
random  by  the  fportive  and  irregular  hand  of 
nature — thofe  of  the  young  Briton,  to  choice  and 
valuable  coI't£tions,  arranged  with  order  and 
elegance,  in  a  well  regulated  and  beautiful  garden. 
The  experiments  of  Valli  appear  to  throw  into 
Jhade,  thofe  of  Fowler  into  light,  the  objects 
which  they  immediately  regard.  From  the  for- 
mer, the  reader  collects  information  with  diffi- 
culty, from  the  latter,  without  labour  or  painful 
attention. 

In 


24o  APPENDIX. 

In  their  deductions  and  fpeculations,  the  two 
preceding  authors  are  no  lefs  diflimilar,  than  with 
regard  to  their  experiments  themfelves.  Valli  is 
more  diffafe  and  often  hypothetical — Fowler  more 
pointed  and  generally  conclufive.  Valli  appears 
to  give  loofened  reins  to  a  glowing  imagination — 
Fowler  to  be  conftantly  under  the  fteady  guidance 
of  a  powerful  and  well-cultivated  underftanding. 
The  former  makes  a  greater  difplay  of  learning, 
and,  therefore,  too  frequently  views  objects 
through  the  more  obfeure  media  of  previous 
publications — the  latter  exhibits  a  higher  degree 
of  ingenuity,  and  derives  the  principal  part  of  his 
information,  not  from  pages,  fan&ioned  only  by 
the  names  of  celebrated,  yet  fallible,  authors,  but 
from  the  great  /b/zo-volume  of  nature,  imprefled 
with  her  own  fignature.  On  the  whole,  Valli 
has  experimented  and  written  in  the  mod  lengthy 
and  profufe — Fowler  in  the  moil  definite  and 
conclufive  manner.  In  many  parts  of  the  writings 
of  the  former,  nothing  elfe  than  the  fiat  of  an 
almighty  genius  would  be  able  to  bring  order  out 
of  confufion — in  thofe  of  the  latter,  lucidity,  con- 
nection, and  regularity,  fhine  pre-eminent  through 
almofl:  every  page. 

Having  thus,  without  referve,   delivered   my 

fentiments  on  the  publications  of  others ',  I  hope  I 

may  be  allowed  to  trefpafs  on  the  reader's  attention 

4  while 


APPENDIX.  241 

while  I  make  a  few  obfervations  relating  to  my 

own. 

1 

Nothing  could  have  induced  me  thus  haftily  to 
forfake  the  humble,  but  fecure,  retreats  of  obfcu- 
rity,  and  rifk  myfelf  before  the  eye  of  the  world 
in  the  hazardous  character  of  an  author,  fave  a 
folicitous  wifh  to  contribute  to  the  advancement 
of  medical  fcience,  and  thus  aid  in  acquiring  for 
man  a  more  effectual  exemption  from  mifery  and 
pain.  I  faw  with  regret  the  literary  trcafures  of 
a  Blumenbach  concealed  from  the  view  of  my 
fellow-citizens  beneath  the  drapery  of  an  ancient 
and  an  obfolete  language.  I  was  anxioufly 
defirous  to  fee  the  phyfiological  fyftem  of  that 
illuftrious  character  completely  clothed  in  the 
language  of  ray  country.  I  engaged  in  the  tranf- 
lation  of  this  work,  not  becaufe  I  conceived  my- 
felf better  qualified  for  its  execution  than  others, 
but  becaufe  others  appeared  to  me  unpardonably 
remifs  with  regard  to  the  undertaking.  The 
execution  proved  laborious  aud  difficult  beyond 
my  expectations.  The  difficulty  of  detecting  an 
author's  precife  meaning  through  the  dulky 
medium  of  a  Latin  expreffion,  can  be  fully  nnder- 
ftood  and  realifed  only  by  him  who  has  made  the 
arduous  experiment. 

vol.  11.  Q^  Even 


i#  APPENDIX. 

Even  after  the  ideas  and  opinions  in  the  original 
are  fully  embraced  and  completely  comprehended, 
another  difficulty  of  no  fmall  magnitude  ftill 
remains,  namely,  to  convey  them  to  the  reader 
with  unequivocal  definitude,  through  the  indefinite 
medium  of  a  different  language.  It  is  well  known 
how  extremely  liable  we  are  to  mifapprehend  the 
precife  meaning  of  an  author  who  even  writes  in 
our  own  vernacular  tongue,  much  more  {o  of  one 
who  publiihes  in  a  language  but  little  ufed  in  con- 
verfaiion,  and,  at  bed,  but  imperfectly  underftood 
by  any  man  living. 

Should  the  foregoing  tranilation  ever  fall  into 
the  hands  of  the  celebrated  profeffor  of  Geottingen, 
I  hope  he  will  receive,  with  candour  and  indul- 
gence, a  well  meant  attempt  to  extend  the  empire 
of  his  utility  and  his  fame,  by  increafing  the 
number  of  his  admiring  readers.  If  the  tranila- 
tion be  in  any  part  erroneous,  in  any  part  defi- 
cient, ftvietures  and  corrections  will  be  thankfully 
received,  and  punctually  attended  to  in  a  fecond 
edition  of  the  work,  fhould  a  fecond  be  demanded 
by  a  patrcHifmg  public.  * 

To  preferve  as  far  as  poflible  the  firm  and 
energetic  fpirit  which  characterizes  the  writings 
of  the  illufirious  profefTor  of  Goettingen,  and  to 

convey 


APPENDIX.  143 

convey  to  my  readers  the  facts,  the  principles,  the 
fpeculations,  and  the  opinions  contained  in  his 
original  work,  without  even  the  (hadow  of  altera- 
tion, diminution,  or  acMition,  has  been  my  (teady 
and  uniform  aim  throughout  the  whole  of  the 
foregoing  tranflation.  Owing,  however,  to  the 
different  conjlituiions  or  idioms,  as  they  ate  more 
generally  termed,  of  the  Latin  and  Englifh  lan- 
guages, my  tranflation  is  in  many  places  far — very 
far  from  Deng  ftriftiy  literal.  Phrafcology  I  con- 
fider,  at  beft,  as  the  mere  trappings  or  drapery  of 
compofifion,  Vs'\\\\c  facls  and  principles  conditute  its 
more  fubitantial  and  important  part.  To  preferve 
the  latter,  therefore,  inviolate,  and  to  communicate 
them  with  the  utmoft  definitude,  is  the  indifpen- 
fible  duty  of  a  tranflator,  from  a  principle  of 
juflice  to  the  original  author,  to  the  public,  and 
to  himfelf  *,  but  in  my  opinion,  he  is  not  bound, 
by  any  principle  whatever,  to  make  an  entire 
facrifice  of  all  elegance  and  beauty,  to  mere  puncti- 
lious literality  of  expreffion.  ImprefTed  with  the 
propriety  and  truth  of  thefe  femiments,  I  have, 
throughout  the  whole  of  the  foregoing  work, 
been  fometimes  literal  and  fometimes  free, 
•accordingly  as  the  one  or  the  other  mode  of 
tranflation  gave  birth  to  a  phrafeology  or  ftile 
mod:  agreeable  to  my  ear,  and  raoft  accordant  to 
the  fpirit  of  the  original  compofition. 

(^2  Witt 


244  APPENDIX. 

With  refpedt  to  the  appendix  itfelf,  it  may  not 
be  amifs  to  make  it  the  fubjedt  of  a  few  tranfient 
obfervations.  The  principle  which  thefe  additi- 
onal pages  regard,  and  are  intended  to  commu- 
nicate, is  juftly  becoming,  among  medical  philofo- 
phers,  an  object  of  primary  importance.  M  his 
principle  opens  to  the  view  of  the  fpeculative  mind 
a  rich  and  fpacious  field,  never  yet  printed,  fave 
by  the  adventurous  fteps  of  a  few  pre  eminently 
active  and  enterprifing  phyfiologifts — A  field,  the 
falutary  fruits  of  which  will,  no  doubt,  at  a  future 
day,  ferve  to  elucidate  the  nature,  to  develope 
the  compofition,  and  to  alleviate  the  complicated 
mifery  of  man. 

My  whole  defign  in  this  appendix  is  to  give  a 
condenfed,  but  fomewhat  general  view,  of  this 
principle  or  influence  difcovered  by  profeflbr  Gal- 
vani. 

By  far  the  greater  number  of  medical  charac- 
ters in  the  immenfe  tract  of  country  embraced 
within  the  limits  of  the  United  States,  are,  in  con- 
fequence  of  their  diftances  from  literary  inftitu- 
tions,  excluded  from  accefs  to  public  libraries, 
and  fruated  quite  beyond  the  free  circulation  of 
phyfical  fcience.  To  fuch  my  appendix  will  ferve 
the  humble  purpofe  of  a  literary  chronicle ;  it  will 
convey  to  them  a  brief  account  of  the  difcoveries 
2  which 


APPENDIX.  24s 

which  are  now  going  forward  in  the  delightful 
and  important  fcience  of  phyfiology. 

On  the  fubject  of  the  influence  difcovered  by 
Galvani  I  have  myfelf  inftituted  and  performed 
a  confiderable  number  of  experiments  *  ;  fome  of 

*  That  the  reader  may  be  acquainted  with  an  eafy,  cheap 
and  familiar  method  of  experimenting  on  this  fubject,  with- 
out having  his  feelings  hurt  by  the  agonizing  pangs  of  tor- 
tured and  dying  animals,  I  will  here  take  the  liberty  of  in- 
ferring, in  form  of  notes,  a  few  extracts  taken  from  a  com- 
munication tranfmitted  to  Mr.  Fowler,  by  his  learned  friend 
Mr.  Robifon,  profdfor  of  natural  philofophy  in  the  univer- 
fity  of  Edinburgh. 

I.  "  I  find  (fays  the  profeflor)  that  if  a  piece  of  zinc  be 
applied  to  the  tongue,  and  be  in  contact  with  a  piece  of  fil- 
ver,  which  touches  any  part  of  the  lining  of  the  mouth, 
noftrils,  ears,  urethra,  or  anus,  the  fenfation  refembling  tafte 
is  felt  on  the  tongue.  If  the  experiment  be  inserted,  by  ap- 
plying the  filver  to  the  tongue,  the  irritation  produced  by 
the  zinc  is  not  fenfible,  except  in  the  mouth  and  the  urethra, 
and  is  very  flight. 

II.  "  If  the  zinc  (finely  poliflied)  be  applied  to  the  ball 
of  the  eye,  the  brightness  of  the  flafh  feems  to  correfpond  with 
the  furface  of  contact  of  the  filver  with  the  tongue,  palate, 
fauces,  or  cheek.  The  fame  tiling  happens  when  the  filver 
is  applied  to  the  eye." 

III.  "  When  a  rod  of  zinc  and  one  of  filver  are  applied 
to  the  roof  of  the  mouth,  as  far  back  as  poffiblc,  the  irrita- 
tions 


246  APPENDIX. 

my  reful ts  hare  appeared  flriking  and  new,  but  my 
experiments  have  been  neither  fufficiently  nume- 
rous nor  varied  to  warrant  the  deduction  and  efta- 
blimment  of  general  principles.  My  prefent  in- 
tention is  ((hould  heaven  indulge  me  in  life  and 
health),    to  profecute  to  fome  extent  this  highly 

tions  produced  by  bringing  their  outer  ends  into  contact,  are 
very  flrong,  and  that  by  the  zinc  reiembles  tafte,  in  the  ,ame 
manner  as  when  applied  to  the  tongue." 

IV.  "  I  had  been  paring  my  toenails  with  fciffars,  and 
had  cut  off  a  confiderable  portion  of  the  th'cic  fkin,  fo  that 
the  blood  began  to  ooze  through  in  the  middle  of  the  wound. 
I  applied  the  zinc  there,  and  an  extenfive  furface  of  filver 
to  the  tongue.  Every  time  I  brought  the  metals  into  con- 
tact, I  felt  a  finait  irritation  by  the  zinc  at  the  wound,"  &c. 

A  variety  of  other  experiments  of  a  fimilar  nature  are 
contained  in  the  fame  communication  from  Mr.  Robifon 
to  Mr.  Fowler ;  but  a  further  detail  of  them  I  conceive  un- 
necefiaxy,  as  the  ingenious  reader,  being  acquainted  with 
the  foregoing,  can  with  facility  devife  other  experiments 
for  himfelf.  Thus  I  have  frequently  conveyed  to  my  eye 
the  luminous  flafh  mentioned  by  Mr.  Robifon,  not  only 
from  die  internal  veftments  of  the  mouth,  the  nofe,  the  ure- 
thra, &c.  but  alfo  from  between  my  fingers,  from  the  cu- 
bital flexure  of  my  arm,  and  from  various  other  parts  of 
my  body,  where  the  texture  of  the  cuticle  and  fkin  is  more 
fine  and  foft  than  ordinary ;  always  taking  care,  however, 
to  moiftcn  the  part  previoufly  to  the  application  of  the 
metals. 

intercfling 


APPENDIX.  347 

interefting  fubject.  Should  my  inveftigation  be 
favoured  with  the  difcovery  of  any  thing  curious 
in  fcience,  or  ufeful  in  practice,  a  detail  of  it  may 
be  expected  in  a  future  communication. 

To  my  folemn  audit  before  the  bar  of  the  pub- 
lic, I  now  ha^en  in  tremulous  anxiety,  "  with  all 
my  imperfections  on  my  head," — imperfections 
which  will  no  doubt  awaken  the  cenfure  of  the 
critic,  but  receive,  I  flatter  myfelf,  the  indulgence 
of  the  liberal  and  candid.  The  approbation  of 
the  former  I  neither  court  nor  regard  ;  that  of 
the  latter  it  (hall  be  my  conflant  ambition  to  de- 
ferve.  The  profeffed  buiinefs  of  moft  modern 
critics  appears  to  be,  to  condemn — promifcuoufly 
condemn,  too  frequently  without  the  fainteft  (ha- 
dow  of  either  inclination  or  talents  to  difcriminate 
merit  from  its  reverfe. 

In  my  view  the  approbation  of  a  profeffed  critic 
is  perfectly  fynonymous  with  the  cenfure  of  the 
liberal  and  the  ingenious,  to  whofe  candid  exami- 
nation the  preceding  pages  are  fubmitted  with  all 
that  refpect  and  deference  due  from  an  inexperi- 
enced writer. 


THE    END. 


612     B056C 


275305 


afe&M^ 


;'^fe: 


